H-Index Leetcode Solution

Problem Statement:

H-Index Leetcode solution says that – Given an array of integers “citations” where citations[i] is the number of citations a researcher received for their i^th paper, return researcher’s H-Index. If several H-Index values are present, return the maximum among them.

Definition of H-Index:  A scientist has an index “h” if h of their n papers have at least h citations each, and the other n-h papers have no more than h citations each.

Example:

Input: 
citations = [3,0,6,1,5]

Output: 
3

Explanation:

citations = [3, 0, 6, 1, 5] means there are  5 papers in total and each of them had received 3, 0, 6, 1, 5 citations respectively. As the researcher has 3 papers with at least 3 citations (3, 6, 5) and the other remaining two with no more than 3 citations (0, 1). So the H-Index will be 3 in this case.

 

Pin

After replacing 6 with n = 5, we have citations = [3,0,5,1,5]. Now, we count the number of papers for each citation number 0 to $5$. The counts are [1,1,0,1,0,2$]$. The first k from right to left (5 down to $0$) that have k<=s is the h-index 3.

 

Pin

cutting off the area with citations more than n

Example 2:

Input: 
citations = [1,3,1]

Output: 1

 

Approach:

Idea:

To solve this problem we use the Counting Sort technique with a little trick.

The idea is to see that the result can only range from 0 to the length of the array (because we can’t have an h-index greater than the total papers published).

1. So we create an array “papers_freq” which acts like a HashMap and loops backward from the highest element.
2.  Then we find “totalCitations ” which is the total number of papers that has more than i citations.
3. We terminate when a total number of papers with more than i citations >= i  (totalCitations >=i ).
4. We don’t need to keep going because we are trying the biggest i possible, we stop and return the result.

 

Code:

C++ code for H-Index Leetcode Solution :

class Solution {
public:
    int hIndex(vector<int>& citations) {
        int len = citations.size();
 
        vector<int> papers_freq(len+1);
        for(int c: citations) {
            if(c > len) {
                papers_freq[len]++;
            } else {
                papers_freq[c]++;
            }
        }

        int totalCitations = 0;
        for(int i = len; i >= 0; i--) {
            totalCitations += papers_freq[i];
            if(totalCitations >= i) {
                return i;
            }   
        }

        return -1;
    }
};

 

Java code for H-Index Leetcode Solution :

class Solution {
    public int hIndex(int[] citations) {
        
        int len = citations.length;
 
        int[] papers_freq = new int[len+1];
        for(int c: citations) {
            if(c > len) {
                papers_freq[len]++;
            } else {
                papers_freq[c]++;
            }
        }

        int totalCitations = 0;
        for(int i = len; i >= 0; i--) {
            totalCitations += papers_freq[i];
            if(totalCitations >= i) {
                return i;
            }   
        }

        return -1;
    }
}

Complexity Analysis for H-Index Leetcoee Solution:

Time Complexity:

The Time Complexity will be O(N), first, we need to traverse the “citations” array once which needs O(N) time. Then for finding the H-Index we need another O(N) since we traverse the papers_freq array at most once. So, we can say that the overall time complexity of the code will be O(N).

Space Complexity:

Space Complexity will be O(N) since we use extra space to store the counts.

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489	Flood Fill LeetCode	182
490	Slowest Key Leetcode Solution	182
491	Kth Largest Element in a Stream Leetcode Solution	182
492	Count and Say	182
493	Reverse a linked list	182
494	Move Zeroes LeetCode Solution	182
495	Remove Minimum Number of Elements Such That no Common Element Exist in both Array	182
496	MiniMax Algorithm	181
497	Number of Steps to Reduce a Number to Zero Leetcode Solution	181
498	Zigzag Conversion LeetCode Solution	181
499	Implement a stack using single queue	181
500	Design Parking System Leetcode Solution	181
501	Longest Common Prefix using Trie	181
502	Length of Last Word Leetcode Solution	181
503	Top View of Binary Tree	181
504	Substring With Concatenation Of All Words	180
505	Jump Game Leetcode Solution	180
506	Intersection of Two Arrays	180
507	Pair with given product	179
508	The Stock Span Problem	179
509	Count and Say Leetcode Solution	179
510	Valid Parenthesis String	179
511	Peak Index in a Mountain Array	179
512	Convert array into Zig-Zag fashion	179
513	Find subarray with given sum (Handles Negative Numbers)	179
514	Contiguous Array Leetcode	178
515	Find N Unique Integers Sum up to Zero Leetcode Solution	178
516	Max Area of Island	178
517	Last Stone Weight	178
518	Find four elements that sum to a given value (Hashmap)	178
519	Longest subarray not having more than K distinct elements	178
520	Mobile Numeric Keypad Problem	178
521	Postfix to Prefix Conversion	178
522	Priority Queue in C++	178
523	Delete Node in a Linked List Leetcode Solution	177
524	Check if a given array contains duplicate elements within k distance from each other	177
525	Shuffle String Leetcode Solution	177
526	N-th Tribonacci Number Leetcode Solution	177
527	Koko Eating Bananas Leetcode Solution	177
528	Prefix to Postfix Conversion	177
529	Find missing elements of a range	177
530	Longest Common Prefix using Sorting	177
531	Shortest Palindrome	176
532	Largest Perimeter Triangle Leetcode Solution	176
533	Find Index of Closing Bracket for a Given Opening Bracket in an Expression	176
534	Relative Sort Array Leetcode Solution	176
535	K-th Distinct Element in an Array	175
536	Isomorphic Strings Leetcode Solution	175
537	Find distinct elements common to all rows of a matrix	175
538	Best Time to Buy and Sell Stock	175
539	Iterative Inorder Traversal of a Binary Tree	175
540	Smallest Subarray With all Occurrences of a Most Frequent Element	174
541	Count number of triplets with product equal to given number	174
542	Is Subsequence Leetcode Solution	174
543	Implementation of Deque using circular array	174
544	First negative integer in every window of size k	174
545	Minimum Operations to convert X to Y	174
546	Implement Stack using Queues	174
547	Change the Array into Permutation of Numbers From 1 to N	174
548	Build Array From Permutation Leetcode Solution	174
549	Excel Sheet Column Title Leetcode Solution	174
550	Container with Most Water	174
551	01 Matrix LeetCode Solution	174
552	Recursion	174
553	Find any one of the multiple repeating elements in read only array	174
554	Hamming Distance	173
555	Convert Sorted Array to Binary Search Tree Leetcode Solution	173
556	Jewels and Stones Leetcode Solution	173
557	Maximum sum rectangle in a 2D matrix	173
558	Distribute Candies to People Leetcode Solution	173
559	Convert a normal BST to Balanced BST	173
560	Remove Linked List Elements Leetcode Solution	173
561	Island Perimeter Leetcode Solution	173
562	Valid Sudoku	173
563	Valid Anagrams	173
564	Find the smallest positive integer value that cannot be represented as sum of any subset of a given array	172
565	Sum of Left Leaves Leetcode Solutions	172
566	Next Greater Frequency Element	172
567	Shuffle an Array	172
568	Linked List Cycle II LeetCode Solution	172
569	Arrange given numbers to form the biggest number	171
570	Assign Cookies Leetcode Solution	171
571	Find Words That Can Be Formed by Characters Leetcode Solution	171
572	Count the number of nodes at given level in a tree using BFS	171
573	Minimum Delete Operations to make all Elements of Array Same	171
574	Check for Balanced Parentheses in an Expression	171
575	Insert Interval Leetcode Solution	171
576	Trapping Rain Water LeetCode Solution	171
577	Shortest Path in a Grid with Obstacles Elimination LeetCode Solution	170
578	3Sum Closest LeetCode Solution	170
579	Maximum path sum in a triangle	170
580	Rotate List Leetcode Solution	170
581	Rearrange a binary string as alternate x and y occurrences	170
582	Summary Ranges Leetcode Solution	170
583	Count all subsequences having product less than K	170
584	Maximum Number of Chocolates to be Distributed Equally Among k Students	170
585	Minimum Bracket Reversals	170
586	Group Multiple Occurrence of Array Elements Ordered by first Occurrence	170
587	Rotate Image LeetCode Solution	170
588	Gold Mine Problem	170
589	Minimum number of distinct elements after removing m items	169
590	Distance Between Bus Stops Leetcode Solution	169
591	The Knapsack Problem	169
592	Combinations Leetcode Solution	169
593	LRU Cache LeetCode Solution	169
594	Permutation in String Leetcode Solution	169
595	Integer to Roman	169
596	Unique Binary Search Trees	168
597	Maximum Distance in Array	168
598	K Empty Slots LeetCode	168
599	Same Tree LeetCode Solution	168
600	Decode Ways	168
601	Minimum Knight Moves LeetCode Solution	168
602	How to check if two given sets are disjoint?	168
603	XOR Operation in an Array Leetcode Solution	167
604	Distance of nearest cell having 1 in a binary matrix	167
605	Printing brackets in Matrix Chain Multiplication Problem	167
606	Segregate 0s and 1s in an Array	167
607	Sieve of Eratosthenes	167
608	Remove All Occurrences of a Substring LeetCode Solution	167
609	Replace Elements with Greatest Element on Right Side Leetcode Solution	167
610	Find the Duplicate Number LeetCode Solution	166
611	Stone Game LeetCode	166
612	Find if an Expression has Duplicate Parenthesis or Not	166
613	Sort Characters By Frequency LeetCode Solution	166
614	License Key Formatting Leetcode Solution	166
615	Best Time to Buy and Sell Stock LeetCode Solution	166
616	Sort Array By Parity LeetCode Solution	166
617	Word Wrap Problem	166
618	Applications of Breadth First Search and Depth First Search	165
619	Maximum difference between first and last indexes of an element in array	165
620	Minimum number of subsets with distinct elements	165
621	Minimum insertions to form a palindrome with permutations allowed	165
622	Find Sum of all unique sub-array sum for a given array	165
623	Frog Jump Leetcode Solution	165
624	Word Pattern	165
625	Find minimum difference between any two elements	165
626	Maximum Consecutive Numbers Present in an Array	164
627	Defanging an IP Address Leetcode Solution	164
628	Smallest Good Base	164
629	Painting Fence Algorithm	164
630	Queries for counts of array elements with values in given range	163
631	Find pairs with given sum such that elements of pair are in different rows	163
632	GCD Of Two Numbers	163
633	Tracking current Maximum Element in a Stack	163
634	Find Maximum Level sum in Binary Tree	163
635	House Robber	163
636	Longest Substring with At Most K Distinct Characters LeetCode Solution	163
637	Minimum Depth of Binary Tree Leetcode Solution	163
638	Best Time to Buy and Sell Stock with Cooldown Leetcode Solution	163
639	Binary Tree Zigzag Level Order Traversal LeetCode Solution	163
640	Check If It Is a Straight Line Leetcode Solution	163
641	Non-overlapping sum of two sets	162
642	Minimum Cost to Hire K Workers	162
643	Isomorphic Strings	162
644	Valid Palindrome II Leetcode Solution	162
645	Employee Free Time LeetCode Solution	162
646	Kth Missing Positive Number Leetcode Solution	162
647	Strobogrammatic Number LeetCode Solution	162
648	Coin Change Problem	162
649	Iterative Method to find Height of Binary Tree	162
650	Maximum Number of Coins You Can Get Leetcode Solution	162
651	Optimal Account Balancing LeetCode Solution	162
652	Print the Fibonacci numbers in reverse order	162
653	Minimum Number of Steps to Make Two Strings Anagram Leetcode Solutions	161
654	Letter Combinations of a Phone Number	161
655	Longest Substring with At Least K Repeating Characters LeetCode Solution	161
656	Delete consecutive same words in a sequence	161
657	Wiggle Sort	161
658	Rearrange an array in order – smallest, largest, 2nd smallest, 2nd largest	161
659	Number of Provinces Leetcode Solution	161
660	Longest Increasing Subsequence	161
661	Count Good Nodes in Binary Tree Leetcode Solution	161
662	Reverse a stack without using extra space in O(n)	160
663	Moving Average from Data Stream Leetcode Solution	160
664	Ugly Number Leetcode Solution	160
665	Merge Two Balanced Binary Search Trees	160
666	Power of Four Leetcode Solution	160
667	K Empty Slots	160
668	Partition Labels LeetCode Solution	160
669	Longest Increasing Path in a Matrix LeetCode Solution	160
670	Maximum Number of Occurrences of a Substring Leetcode Solution	160
671	Number of Dice Rolls With Target Sum LeetCode Solution	160
672	Sum of All Odd Length Subarrays Leetcode Solution	160
673	Find the Distance Value Between Two Arrays Leetcode Solution	159
674	Check If Two String Arrays are Equivalent Leetcode Solution	159
675	Convert an array to reduced form	159
676	BFS vs DFS for Binary Tree	159
677	Form minimum number from given sequence	159
678	Sort Array by Increasing Frequency Leetcode Solution	159
679	Valid Perfect Square Leetcode Solution	159
680	Edit Distance LeetCode Solution	158
681	String to Integer (atoi) LeetCode Solution	158
682	Check if a queue can be sorted into another queue using a stack	158
683	Flipping an Image LeetCode Solution	158
684	Reducing Dishes LeetCode Solution	158
685	Find the Smallest Divisor given a Threshold Leetcode Solution	158
686	Path With Maximum Minimum Value LeetCode Solution	158
687	Reverse Only Letters LeetCode Solution	158
688	Largest Sum Contiguous Subarray	158
689	Remove Invalid Parentheses Leetcode Solution	158
690	Unique Paths II Leetcode Solution	158
691	How to Create Mergable Stack?	157
692	Robot Room Cleaner Leetcode Solution	157
693	Merge Two Binary Trees LeetCode Solution	157
694	Populating Next Right Pointers in Each Node	157
695	Maximum Product of Two Elements in an Array Leetcode Solution	157
696	Binary Tree zigzag level order Traversal	157
697	Permutation Sequence LeetCode Solution	157
698	Construct BST from given Preorder Traversal	157
699	Find Leaves of Binary Tree LeetCode Solution	157
700	Convert a Number to Hexadecimal Leetcode Solution	157
701	To Lower Case Leetcode Solution	157
702	Increasing Decreasing String Leetcode Solution	157
703	Reversing a Queue using Recursion	157
704	Lucky Numbers in a Matrix Leetcode Solution	157
705	Reorganize String	157
706	Reservoir Sampling	157
707	Delete Nth node from the end of the given linked list	157
708	Find Largest d in Array such that a + b + c = d	157
709	Sum of f(a[i], a[j]) over all pairs in an array of n integers	157
710	Inorder Successor of a node in Binary Tree	157
711	Find whether an array is subset of another array	157
712	Dynamic Programming Basics	157
713	Subset Sum Leetcode	157
714	Partition Array Into Three Parts With Equal Sum Leetcode Solution	156
715	Keyboard Row Leetcode Solution	156
716	Restore IP Addresses Leetcode Solution	156
717	Majority Element II Leetcode Solution	156
718	Recover Binary Search Tree	156
719	Factorial Trailing Zeroes Leetcode Solution	156
720	Valid Palindrome	156
721	Add and Search Word – Data structure design LeetCode	155
722	Bulb Switcher LeetCode Solution	155
723	Decompress Run-Length Encoded List Leetcode Solution	155
724	Find the node with minimum value in a Binary Search Tree	155
725	Hamming Distance Leetcode Solution	154
726	Search a 2D Matrix II Leetcode Solution	154
727	Maximum Product of Three Numbers LeetCode Solution	154
728	Student Attendance Record I Leetcode Solution	154
729	Rank Transform of an Array Leetcode Solution	154
730	Finding K closest element	154
731	First Unique Character in a String LeetCode Solution	154
732	Minimum Distance Between BST Nodes Leetcode Solution	153
733	Minimum Cost For Tickets Leetcode Solution	153
734	Sorted Linked List to Balanced BST	153
735	Evaluate Reverse Polish Notation LeetCode Solution	153
736	Find the largest multiple of 3	153
737	Morris Traversal	153
738	Invert Binary Tree LeetCode Solution	153
739	Symmetric Tree Leetcode Solution	153
740	Find Median from Data Stream LeetCode Solution	153
741	Word Pattern LeetCode Solution	153
742	Bubble sort using two Stacks	153
743	String Compression LeetCode Solution	153
744	Find unique character in a string	153
745	Maximum 69 Number Leetcode Solution	153
746	Stack Permutations (Check if an array is stack permutation of other)	153
747	Queue based approach for first non-repeating character in a stream	153
748	Diagonal Traversal of Binary Tree	153
749	Numbers with prime frequencies greater than or equal to k	153
750	Maximum Depth of N-ary Tree Leetcode Solution	153
751	Perform String Shifts Leetcode	152
752	Largest rectangular sub-matrix whose sum is 0	152
753	Longest Span with same Sum in two Binary arrays	152
754	Number of Islands II LeetCode Solution	152
755	Generate all possible sorted arrays from alternate elements of two given sorted arrays	152
756	Largest subarray with equal number of 0s and 1s	152
757	Best Meeting Point LeetCode Solution	152
758	Non-decreasing Array LeetCode Solution	152
759	Snakes and Ladders LeetCode Solution	152
760	Maximum Length of a Concatenated String with Unique Characters Leetcode Solution	152
761	Binary Tree Maximum Path Sum LeetCode Solution	152
762	Binomial Coefficient	152
763	Find All Duplicates in an Array LeetCode Solution	152
764	Minimum Height Trees	152
765	Search in a Binary Search Tree Leetcode Solution	152
766	Deletion in a Binary Tree	152
767	Elements to be added so that all elements of a range are present in array	152
768	k-th missing element in increasing sequence which is not present in a given sequence	151
769	Find Maximum Depth of Nested Parenthesis in a String	151
770	Largest Rectangle in Histogram LeetCode Solution	151
771	Remove Duplicates from Sorted List LeetCode Solution	151
772	N-Queens LeetCode Solution	151
773	Split a String in Balanced Strings Leetcode Solution	151
774	Jump Game	151
775	Race Car LeetCode Solution	151
776	Kth ancestor of a node in binary tree	151
777	Merge K Sorted Linked Lists	151
778	Check If Array Pairs Are Divisible by k LeetCode Solution	151
779	Linked List Cycle	151
780	Minimum number of jumps to reach end	150
781	Find if Path Exists in Graph Leetcode Solution	150
782	Maximum Difference Between Increasing Elements LeetCode Solution	150
783	Remove Nth Node From End of List Leetcode Solution	150
784	Find Pair with Greatest Product in Array	150
785	Minimize Maximum Pair Sum in Array LeetCode Solution	150
786	Final Prices With a Special Discount in a Shop Leetcode Solution	150
787	Count quadruples from four sorted arrays whose sum is equal to a given value x	150
788	Special Array With X Elements Greater Than or Equal X Leetcode Solution	150
789	Transpose Graph	150
790	Alien Dictionary LeetCode Solution	149
791	Growable array based stack	149
792	Relative Ranks Leetcode Solution	149
793	Number of NGEs to the Right	149
794	Can Place Flowers LeetCode Solution	149
795	Nearest Exit from Entrance in Maze LeetCode Solution	149
796	Nested List Weight Sum II LeetCode Solution	148
797	Merge Sorted Array LeetCode Solution	148
798	Interval Tree	148
799	Get Maximum in Generated Array Leetcode Solution	148
800	Check for Palindrome after every character replacement Query	148
801	Minimum time required to rot all oranges	148
802	Tiling Problem	148
803	Check if Two Expressions With Brackets are Same	148
804	Print a Binary Tree in Vertical Order	148
805	Valid Number	148
806	Minimum Jumps to Reach Home LeetCode Solution	148
807	Sort an array according to the order defined by another array	148
808	Remove brackets from an algebraic string containing + and – operators	148
809	String comparison containing wildcards	148
810	Program for Bridge and Torch problem	148
811	Minimum Time Visiting All Points Leetcode Solution	148
812	Crawler Log Folder Leetcode Solution	148
813	Convert BST to Min Heap	148
814	Number Complement Leetcode Solution	148
815	Friends Pairing Problem	147
816	Total Numbers With no Repeated Digits in a Range	147
817	Sort Colors	147
818	Subarray Product Less Than K LeetCode Solution	147
819	Check if a given array can represent Preorder Traversal of Binary Search Tree	147
820	Count items common to both the lists but with different prices	147
821	Regular Expression Matching	147
822	Sort Array By Parity II Leetcode Solution	147
823	Top K Frequent Words LeetCode Solution	147
824	Base 7 Leetcode Solution	147
825	Partition to K Equal Sum Subsets Leetcode Solution	147
826	Reorder Data in Log Files LeetCode Solution	147
827	Priority Queue using doubly linked list	147
828	Find the Only Repetitive Element Between 1 to N-1	147
829	Remove Duplicates from Sorted List II	147
830	Maximum Profit in Job Scheduling Leetcode Solution	147
831	Design a Stack With Increment Operation Leetcode Solution	147
832	One Edit Distance LeetCode Solution	147
833	Maximum size subarray sum equals k	147
834	Make Two Arrays Equal by Reversing Sub-arrays Leetcode Solution	147
835	A Space Optimized DP solution for 0-1 Knapsack Problem	147
836	Longest Subarray Having Count of 1s One More than Count of 0s	146
837	Minimum swaps to make sequences increasing	146
838	Circular Queue	146
839	Minimum Number of Taps to Open to Water a Garden LeetCode Solution	146
840	Path with maximum average value	146
841	Partition List Leetcode Solution	145
842	Sorted Array to Balanced BST	145
843	Guess Number Higher or Lower LeetCode Solution	145
844	Given an Array of Pairs Find all Symmetric Pairs in it	145
845	Brightest Position on Street LeetCode Solution	145
846	Find the subarray with least average	145
847	Clone Graph LeetCode Solution	145
848	Subset with sum divisible by m	145
849	Binary Search Tree Search and Insertion	145
850	Subsequence of Size K With the Largest Even Sum LeetCode Solution	145
851	Check if an Array is Stack Sortable	144
852	Three way partitioning of an array around a given range	144
853	Level order Traversal in Spiral Form	144
854	Iterative Preorder Traversal	144
855	Brick Wall LeetCode Solution	144
856	Repeated Substring Pattern LeetCode Solution	144
857	Insert into a Binary Search Tree Leetcode Solution	144
858	Course Schedule II – LeetCode	144
859	Tree Traversal (Preorder, Inorder & Postorder)	144
860	Maximum Nesting Depth of the Parentheses Leetcode Solution	144
861	Valid Parentheses Leetcode Solution	144
862	Find All Possible Recipes from Given Supplies LeetCode Solution	144
863	Minimum Sum Path in a Triangle	144
864	Last Stone Weight II LeetCode Solution	144
865	Count Distinct Elements in Every Window of Size K	144
866	Sum of nearest smaller and greater number	144
867	Minimum Swaps to Make Strings Equal Leetcode Solution	144
868	Union and Intersection of two Linked Lists	144
869	Find all triplets with zero sum	143
870	Permutation Coefficient	143
871	Water Bottles Leetcode Solution	143
872	Check whether a given Binary Tree is Complete or not	143
873	Daily Temperatures Leetcode Solution	143
874	Count ways to reach the nth stair using step 1, 2 or 3	143
875	Rearrange Spaces Between Words Leetcode Solution	143
876	LCS (Longest Common Subsequence) of three strings	142
877	Best Time to Buy and Sell Stock with Transaction Fee Leetcode Solution	142
878	Missing Element in Sorted Array LeetCode Solution	142
879	Spiral Matrix II Leetcode Solution	142
880	4Sum	142
881	Destination City Leetcode Solution	142
882	Balanced Expression with Replacement	142
883	Range sum queries without updates	142
884	Robot Bounded In Circle LeetCode Solution	142
885	Lemonade Change Leetcode Solution	142
886	GCDs of given index ranges in an array	142
887	Guess Number Higher or Lower II	142
888	Least Number of Unique Integers after K Removals Leetcode Solution	142
889	Form Minimum Number From Given Sequence	142
890	Number of Days Between Two Dates LeetCode Solution	142
891	Sequences of given length where every element is more than or equal to twice of previous	142
892	Matrix Chain Multiplication	142
893	Count Negative Numbers in a Sorted Matrix LeetCode Solution	142
894	Identify and Mark Unmatched Parenthesis in an Expression	141
895	Minimum sum of multiplications of n numbers	141
896	Design Browser History LeetCode Solution	141
897	BFS for Disconnected Graph	141
898	Queries for GCD of all numbers of an array except elements in a given range	141
899	An Interesting Method to generate Binary Numbers from 1 to n	141
900	Delete And Earn	141
901	Palindrome Partitioning Leetcode Solution	141
902	Maximum Score After Splitting a String Leetcode Solution	140
903	Convert Sorted List to Binary Search Tree	140
904	Spiral Matrix III LeetCode Solution	140
905	Find Maximum Sum Possible Equal Sum of Three Stacks	140
906	Intersection of Two Linked Lists LeetCode Solution	140
907	Diagonal Traversal LeetCode Solution	140
908	Strongly Connected Component	140
909	Time Based Key-Value Store LeetCode Solution	140
910	Find distance between two nodes of a Binary Tree	140
911	Distinct adjacent elements in an array	140
912	Shortest Word Distance Leetcode Solution	140
913	Special Positions in a Binary Matrix Leetcode Solution	140
914	Find all permuted rows of a given row in a matrix	140
915	Check if the given array can represent Level Order Traversal of Binary Search Tree	140
916	Count Subarrays with Same Even and Odd Elements	140
917	Insert Delete GetRandom	140
918	Construct Complete Binary Tree from its Linked List Representation	140
919	Rearrange Array such that arr[i] >= arr[j] if i is even and arr[i] <= arr[j] if i is odd and j < i	139
920	Find Common Characters Leetcode Solution	139
921	Lexicographical Numbers Leetcode Solution	139
922	Diagonal Traverse LeetCode Solution	139
923	Remove Duplicates from Sorted List II LeetCode Solution	139
924	Trim a Binary Search Tree	139
925	Rearrange an Array Such that arr[i] is equal to i	139
926	A program to check if a binary tree is BST or not	139
927	Merge Two Sorted Lists Leetcode	139
928	Alien Dictionary	139
929	Check if stack elements are pairwise consecutive	139
930	Set Matrix Zeroes Leetcode Solution	139
931	Word Break	138
932	Iterative Postorder Traversal Using Two Stacks	138
933	Analyze User Website Visit Pattern LeetCode Solution	138
934	Longest Palindromic Subsequence	138
935	3 Sum	138
936	Number of Distinct Islands Leetcode Solution	138
937	Merging Intervals	138
938	Maximum Frequency Stack Leetcode Solution	138
939	K’th Largest Element in BST when modification to BST is not allowed	138
940	Range LCM Queries	138
941	Print Fibonacci sequence using 2 variables	138
942	Vertical sum in a given binary tree	138
943	Collect maximum points in a grid using two traversals	138
944	Count Submatrices With All Ones LeetCode Solution	137
945	All Unique Triplets that Sum up to a Given Value	137
946	Construct BST from its given Level Order Traversal	137
947	Count pair with Given Sum	137
948	Queue using Stacks	137
949	Construct the Rectangle Leetcode Solution	137
950	Infix to Postfix	137
951	Longest Nice Substring LeetCode Solution	137
952	Can Make Arithmetic Progression From Sequence Leetcode Solution	137
953	Three Consecutive Odds Leetcode Solution	137
954	Stone Game II Leetcode	137
955	Binary Tree Longest Consecutive Sequence LeetCode Solution	136
956	Number of Equivalent Domino Pairs Leetcode Solution	136
957	Maximize Sum of Array after K Negations Leetcode Solution	136
958	Minimum Height Trees LeetCode Solution	136
959	Dividing Array into Pairs With Sum Divisible by K	136
960	Largest area rectangular sub-matrix with equal number of 1’s and 0’s	136
961	Maximum Subarray Sum Excluding Certain Elements	136
962	Sliding Window Maximum	136
963	Reverse Nodes in K-Group	136
964	Level order traversal using two Queues	136
965	Averages of Levels in Binary Tree	136
966	Palindrome Partitioning	136
967	Product of Array Except Self LeetCode Solution	136
968	Check if any two intervals overlap among a given set of intervals	135
969	Count Primes in Ranges	135
970	K Closest Points to Origin Leetcode Solution	135
971	Maximum Product of Indexes of Next Greater on Left and Right	135
972	Binary array after M range toggle operations	135
973	Breadth First Search (BFS) for a Graph	135
974	Difference Array | Range update query in O(1)	135
975	Pattern Occurrences using Stack	135
976	Find postorder traversal of BST from preorder traversal	135
977	Median of Two Sorted Arrays	135
978	Asteroid Collision LeetCode Solution	135
979	Split Array Into Consecutive Subsequences	135
980	Create Maximum Number	135
981	Find Maximum of Minimum for Every Window Size in a Given Array	134
982	Level Order Traversal of Binary Tree	134
983	Maximum subsequence sum such that no three are consecutive	134
984	Check If a Word Occurs As a Prefix of Any Word in a Sentence Leetcode Solution	134
985	Minesweeper LeetCode Solution	134
986	Height of a generic tree from parent array	134
987	Newman-Conway Sequence	134
988	Segment Tree	134
989	Kth Smallest Element in a BST Leetcode Solution	134
990	Largest divisible pairs subset	134
991	Symmetric Tree	134
992	The Maze III LeetCode Solution	134
993	Maximum Product Subarray	134
994	Largest Substring Between Two Equal Characters Leetcode Solution	134
995	Depth First Search (DFS) for a Graph	133
996	Find Duplicate Subtrees	133
997	Serialize and Deserialize Binary Tree	133
998	Length of Longest Fibonacci Subsequence	133
999	Decrypt String from Alphabet to Integer Mapping Leetcode Solution	133
1000	The Painter’s Partition Problem	133
1001	Build an Array With Stack Operations Leetcode Solution	133
1002	Friends Of Appropriate Ages LeetCode Solution	133
1003	Rearrange array such that even positioned are greater than odd	133
1004	Next Greater Element III LeetCode Solution	133
1005	Find the Difference Leetcode Solution	133
1006	First missing positive	133
1007	Maximum Number of Ways to Partition an Array LeetCode Solution	133
1008	Unique Paths II	133
1009	Maximum Length of Repeated Subarray	133
1010	Shuffle 2n integers as a1-b1-a2-b2-a3-b3-..bn without using extra space	133
1011	Binary Search Tree Delete Operation	133
1012	Sign of the Product of an Array LeetCode Solution	133
1013	Kill Process LeetCode Solution	133
1014	Climbing stairs	132
1015	My Calendar I LeetCode Solution	132
1016	Longest subsequence such that difference between adjacents is one	132
1017	Count subarrays where second highest lie before highest	132
1018	Find the First Circular Tour that visits all the Petrol Pumps	132
1019	Find number of pairs in an array such that their XOR is 0	132
1020	Boundary Traversal of binary tree	132
1021	Number Of Longest Increasing Subsequence	132
1022	Insertion in a Binary Tree	132
1023	Graph Valid Tree LeetCode Solution	132
1024	Balanced Binary Tree	132
1025	Design Hit Counter LeetCode Solution	131
1026	Validate Binary Search Tree	131
1027	Advantages of BST over Hash Table	131
1028	Largest Number Leetcode Solution	131
1029	Double the first element and move zero to end	131
1030	Super Ugly Number	131
1031	Move all negative elements to end in order with extra space allowed	131
1032	Construct Binary Tree from given Parent Array representation	131
1033	Make The String Great Leetcode Solution	131
1034	Partition Equal Subset Sum	131
1035	Morris Inorder Traversal	131
1036	Valid Boomerang Leetcode Solution	131
1037	Implement Trie (Prefix Tree) Leetcode Solution	130
1038	Shortest Completing Word Leetcode Solution	130
1039	Boolean Parenthesization Problem	130
1040	Recover Binary Search Tree Leetcode Solution	130
1041	Add two numbers	130
1042	Ugly Numbers	130
1043	Compute nCr % p	130
1044	Bitwise AND of Numbers Range LeetCode Solution	129
1045	Available Captures for Rook Leetcode Solution	129
1046	Maximum difference between frequency of two elements such that element having greater frequency is also greater	129
1047	Rearrange an array such that ‘arr[j]’ becomes ‘i’ if ‘arr[i]’ is ‘j’	129
1048	String Matching in an Array Leetcode Solution	129
1049	Minimum Index Sum of Two Lists	129
1050	Generate Parentheses Leetcode Solution	129
1051	Employee Importance LeetCode Solution	129
1052	Kth Smallest Element in a Sorted Matrix LeetCode Solution	129
1053	Binary Search Tree	129
1054	Count minimum steps to get the given desired array	129
1055	Minimum Size Subarray Sum	129
1056	Ugly Number II LeetCode Solution	129
1057	Scramble String LeetCode Solution	128
1058	Defanging an IP Address LeetCode Solution	128
1059	Construction of Longest Increasing Subsequence (N log N)	128
1060	Populating Next Right Pointers in Each Node Leetcode Solution	128
1061	Find Peak Element	128
1062	Maximum length subsequence with difference between adjacent elements as either 0 or 1	128
1063	Invalid Transactions LeetCode Solution	128
1064	Maximum Sum of 3 Non-Overlapping Subarrays	128
1065	Binary Tree Right Side View LeetCode Solution	128
1066	Determine Whether Matrix Can Be Obtained By Rotation LeetCode Solution	128
1067	Combination Sum IV LeetCode Solution	128
1068	Find whether a subarray is in form of a mountain or not	128
1069	Longest Bitonic Subsequence	128
1070	Maximize Distance to Closest Person LeetCode Solution	128
1071	Number of palindromic paths in a matrix	128
1072	Regular Expression Matching Regular Expression Matching LeetCode Solution	127
1073	Iterative Depth First Traversal of Graph	127
1074	Maximum weight transformation of a given string	127
1075	Remove Palindromic Subsequences Leetcode Solution	127
1076	Search in Sorted Rotated Array	127
1077	Increasing Triplet Subsequence LeetCode Solution	127
1078	Number of Students Doing Homework at a Given Time Leetcode Solution	127
1079	Clone a Binary Tree with Random Pointers	127
1080	Find a Peak Element II LeetCode Solution	127
1081	Constant time range add operation on an array	127
1082	Lowest Common Ancestor	126
1083	Remove Duplicates from Sorted Array II Leetcode Solution	126
1084	Day of the Year Leetcode Solution	126
1085	Find the minimum distance between two numbers	126
1086	Smallest Common Region Leetcode Solution	126
1087	Number of Closed Islands Leetcode Solution	126
1088	Count pairs from two sorted arrays whose sum is equal to a given value x	126
1089	Custom Sort String Leetcode Solution	126
1090	Divisible Pairs Counting	126
1091	Path Sum II LeetCode Solution	126
1092	Types of Binary Tree	125
1093	Number of siblings of a given Node in n-ary Tree	125
1094	Path Sum	125
1095	Largest BST Subtree LeetCode Solution	125
1096	Find maximum difference between nearest left and right smaller elements	125
1097	Print Next Greater Number of Q queries	125
1098	Next Permutation Leetcode Solution	125
1099	Distinct Subsequences	125
1100	Print all triplets in sorted array that form AP	125
1101	Rearrange array such that even index elements are smaller and odd index elements are greater	125
1102	Binary Tree Data Structure	125
1103	Kth Smallest Product of Two Sorted Arrays LeetCode Solution	125
1104	Serialize and Deserialize Binary Tree LeetCode Solution	125
1105	Write Code to Determine if Two Trees are Identical	124
1106	Root to Leaf path with target sum Leetcode Solutions	124
1107	Minimum Absolute Difference in BST Leetcode Solution	124
1108	Bottom View of a Binary Tree	124
1109	Find Smallest Range Containing Elements from k Lists	124
1110	Subarrays with K Different Integers Leetcode Solution	124
1111	Consecutive Characters LeetCode Solution	124
1112	Level of Each node in a Tree from source node	124
1113	Find Three Element From Different Three Arrays Such That a + b + c = sum	124
1114	Third Maximum Number Leetcode Solution	123
1115	Print Right View of a Binary Tree	123
1116	Longest Subarray of 1’s After Deleting One Element LeetCode Solution	123
1117	Construct Binary Tree from Preorder and Postorder Traversal LeetCode Solution	123
1118	Remove duplicates from sorted array	123
1119	Cells with Odd Values in a Matrix LeetCode Solution	123
1120	Subset Sum Problem in O(sum) space	123
1121	Topological Sorting	123
1122	Products of ranges in an array	123
1123	Cutting a Rod	123
1124	Reformat The String Leetcode Solution	122
1125	Queries for Number of Distinct Elements in a Subarray	122
1126	Palindrome Permutation LeetCode Solution	122
1127	Closest Binary Search Tree Value Leetcode Solution	122
1128	Maximum Product Subarray	122
1129	Maximum Binary Tree	122
1130	Convert BST into a Min-Heap without using array	122
1131	K maximum sums of overlapping contiguous sub-arrays	122
1132	Count Largest Group Leetcode Solution	121
1133	Iterative method to find ancestors of a given binary tree	121
1134	Valid Tic-Tac-Toe State LeetCode Solution	121
1135	Search an Element in Sorted Rotated Array	121
1136	Minimum Score Triangulation of Polygon Leetcode Solution	121
1137	Mean of Array After Removing Some Elements Leetcode Solution	121
1138	Diameter of N-Ary Tree LeetCode Solution	121
1139	Print modified array after executing the commands of addition and subtraction	121
1140	Construct K Palindrome Strings LeetCode Solution	120
1141	Prime Palindrome LeetCode Solution	120
1142	Find a sorted subsequence of size 3 in linear time	120
1143	Golomb sequence	120
1144	Moser-de Bruijn Sequence	120
1145	Sum of Even Numbers After Queries	120
1146	Thousand Separator Leetcode Solution	120
1147	Kth Smallest Number in Multiplication Table Leetcode Solution	120
1148	Minimum sum of squares of character counts in a given string after removing k characters	120
1149	Search Insert Position	120
1150	Factorial Trailing Zeroes LeetCode Solution	119
1151	Find maximum length Snake sequence	119
1152	Red-Black Tree Introduction	119
1153	Longest Increasing Consecutive Subsequence	119
1154	Merge two BSTs with limited extra space	119
1155	Find Two Non-overlapping Sub-arrays Each With Target Sum LeetCode Solution	119
1156	Maximum Product of Splitted Binary Tree LeetCode Solution	118
1157	Possible Bipartition LeetCode Solution	118
1158	Compare Strings by Frequency of the Smallest Character Leetcode Solution	118
1159	Transform a BST to Greater sum Tree	118
1160	Swapping Nodes in a Linked List Leetcode Solution	118
1161	Delete Nodes and Return Forest Leetcode Solution	118
1162	Palindromic Substrings Leetcode Solution	118
1163	Binary Tree to Binary Search Tree Conversion	118
1164	Decrease Elements To Make Array Zigzag LeetCode Solution	118
1165	Find the smallest binary digit multiple of given number	118
1166	Bus Routes Leetcode Solution	118
1167	Minimum Sideway Jumps LeetCode Solution	118
1168	Maximize sum of consecutive differences in a circular array	117
1169	Check Array Formation Through Concatenation Leetcode Solution	117
1170	Priority Queue	117
1171	Swap Nodes In Pairs	117
1172	Number of Orders in the Backlog Leetcode Solution	117
1173	Count Pairs Whose Products Exist in Array	117
1174	Longest Repeated Subsequence	117
1175	Decision Tree	117
1176	Minimum Cost to Move Chips to The Same Position LeetCode Solution	117
1177	Count even length binary sequences with same sum of first and second half bits	117
1178	Rotate Array	117
1179	Matchsticks to Square Leetcode Solution	117
1180	K’th Largest element in BST using constant extra space	117
1181	Find Largest Value in Each Tree Row LeetCode Solution	116
1182	Minimum Moves to Equal Array Elements LeetCode Solution	116
1183	Web Crawler LeetCode Solution	116
1184	Given a binary tree, how do you remove all the half nodes?	115
1185	Contiguous Array LeetCode Solution	115
1186	Maximum sum bitonic subarray	115
1187	Closest Leaf in a Binary Tree LeetCode Solution	115
1188	Remove Max Number of Edges to Keep Graph Fully Traversable Leetcode Solution	115
1189	First Bad Version	115
1190	Search Suggestions System LeetCode Solution	115
1191	Array Queries for multiply replacements and product	114
1192	Moving Stones Until Consecutive Leetcode Solution	114
1193	Divide Two Integers Leetcode Solution	114
1194	Queue Reconstruction by Height	114
1195	Integer Break LeetCode Solution	114
1196	Reformat Date LeetCode Solution	113
1197	Kth Smallest Element in a BST	113
1198	Reverse a Path in BST using Queue	113
1199	How to print maximum number of A’s using given four keys	113
1200	Convert Sorted Array to Binary Search Tree LeetCode Solutions	113
1201	Maximum number of segments of lengths a, b and c	113
1202	Maximum Depth Of Binary Tree	113
1203	Maximum sum of pairs with specific difference	113
1204	Sum of Left Leaves LeetCode Solution	113
1205	Lowest Common Ancestor in Binary Search Tree	113
1206	Valid Triangle Number	113
1207	Champagne Tower LeetCode Solution	113
1208	Write a function to get the intersection point of two Linked Lists	112
1209	Longest Common Prefix Using Word by Word Matching	112
1210	Filter Restaurants by Vegan-Friendly, Price and Distance Leetcode Solution	112
1211	Replace two consecutive equal values with one greater	112
1212	Range Sum Query using Sparse Table	112
1213	Lowest Common Ancestor of a Binary Tree Leetcode Solution	112
1214	Guess The Word	112
1215	Range Queries for Longest Correct Bracket Subsequence	111
1216	Convert Integer to the Sum of Two No-Zero Integers Leetcode Solution	111
1217	Maximize Elements Using Another Array	111
1218	New 21 Game	111
1219	LRU Cache Leetcode Solution	111
1220	Graph and its representation	111
1221	Flatten 2D Vector LeetCode Solution	111
1222	Print modified array after multiple array range increment operations	111
1223	Check Completeness of a Binary Tree LeetCode Solution	111
1224	Print n terms of Newman-Conway Sequence	111
1225	Symmetric Tree LeetCode Solution Leetcode Solution	111
1226	Path Crossing Leetcode Solution	110
1227	Queries on Probability of Even or Odd Number in given Ranges	110
1228	Maximum Value at a Given Index in a Bounded Array LeetCode Solution	110
1229	Valid Perfect Square LeetCode Solution	110
1230	Concatenation of Array LeetCode Solution	110
1231	Design Skiplist LeetCode Solution	110
1232	Largest Plus Sign Leetcode Solution	110
1233	Check if each internal node of a BST has exactly one child	110
1234	Arithmetic Slices II – Subsequence LeetCode Solution	110
1235	Missing Number	109
1236	Sliding Window Median Leetcode Solution	109
1237	Graph Cloning	109
1238	The kth Factor of n Leetcode Solution	109
1239	Check if all levels of two Binary Tree are anagrams or not	109
1240	Find Minimum in Rotated Sorted Array II LeetCode Solution	109
1241	BST to a Tree with Sum of all Smaller Keys	109
1242	Maximum Array from Two given Arrays Keeping Order Same	109
1243	Maximum sum of a path in a Right Number Triangle	109
1244	Merge Sort	109
1245	Minimum Swaps To Make Sequences Increasing LeetCode Solution	109
1246	Perfect Squares LeetCode Solution	109
1247	Check for Identical BSTs without building the trees	109
1248	Smallest Range II Leetcode Solution	108
1249	Mean of range in array	108
1250	Count Subsets Having Distinct Even Numbers	108
1251	Bold Words in String LeetCode Solution	108
1252	Parallel Courses II LeetCode Solution	108
1253	Power of Two	108
1254	Count and Toggle Queries on a Binary Array	108
1255	Min Cost Climbing Stairs LeetCode Solution	107
1256	Image Overlap LeetCode Solution	107
1257	Find minimum number of merge operations to make an array palindrome	107
1258	Contiguous Array	107
1259	Maximum Product Subarray	107
1260	Check If a String Can Break Another String Leetcode Solution	106
1261	Minimum Remove to Make Valid Parentheses LeetCode Solution	106
1262	Excel Sheet Column Title LeetCode Solution	106
1263	Next greater element	105
1264	Verify Preorder Serialization of a Binary Tree	105
1265	Find k-th smallest element in BST (Order Statistics in BST)	105
1266	Number of elements less than or equal to a given number in a given subarray	104
1267	Palindrome Partitioning	104
1268	Print Ancestors of a Given Binary Tree Node Without Recursion	104
1269	Merge k Sorted Lists Leetcode Solution	104
1270	Peeking Iterator LeetCode Solution	104
1271	Minimum Time to Collect All Apples in a Tree LeetCode Solution	103
1272	Orderly Queue LeetCode Solution	103
1273	Merge Sorted Array	102
1274	Check if two nodes are on the same path in a Tree	102
1275	Check in binary array the number represented by a subarray is odd or even	102
1276	Newman–Shanks–Williams prime	102
1277	Different Ways to Add Parentheses Leetcode Solution	100
1278	Koko Eating Bananas LeetCode Solution	100
1279	Check if X can give change to every person in the Queue	99
1280	Largest Submatrix With Rearrangements LeetCode Solution	98
1281	Find maximum average subarray of k length	98
1282	Longest Substring Without Repeating Characters Leetcode Solution	98
1283	Maximum Sum Increasing Subsequence	98
1284	Arranging Coins Leetcode Solution	98
1285	Minimum Total Space Wasted With K Resizing Operations LeetCode Solution	97
1286	Range Minimum Query (Square Root Decomposition and Sparse Table)	97
1287	Minimum Number of People to Teach LeetCode Solution	96
1288	Number of indexes with equal elements in given range	96
1289	Queries for Decimal Values of Subarrays of a Binary Array	96
1290	Array Nesting Leetcode Solution	96
1291	Maximum product of an increasing subsequence	95
1292	Convert to Base -2 LeetCode Solution	94
1293	Check given array of size n can represent BST of n levels or not	94
1294	Binary Tree to Binary Search Tree Conversion using STL set	94
1295	Jump Game IV LeetCode Solution	93
1296	Find the Winner of the Circular Game LeetCode Solution	93
1297	Convert a BST to a Binary Tree such that sum of all greater keys is added to every key	93
1298	Minimum Possible Integer After at Most K Adjacent Swaps On Digits LeetCode Solution	93
1299	Random Pick Index LeetCode Solution	93
1300	Queries on XOR of greatest odd divisor of the range	92
1301	Add Two Numbers II Leetcode Solution	92
1302	Encoded String With Shortest Length LeetCode Solution	92
1303	Reach a Number LeetCode Solution	92
1304	Continuous Subarray Sum LeetCode Solution	91
1305	Insert Delete GetRandom O(1) Leetcode Solution	90
1306	Number of Subsequences That Satisfy the Given Sum Condition LeetCode solution	90
1307	Vertical Order Traversal of Binary Tree LeetCode Solution	89
1308	Palindrome Number LeetCode Solution	89
1309	Design Underground System Leetcode Solution	88
1310	Print Maximum Length Chain of Pairs	86
1311	Detect Capital Leetcode Solution	83
1312	Design A Leaderboard Leetcode Solution	83
1313	Substring with Concatenation of All Words Leetcode Solution	80
1314	Top K Frequent Elements LeetCode Solution	79
1315	Minimum Swaps to Group All 1’s Together Leetcode Solution	78
1316	Count Sub Islands LeetCode Solution	76
1317	Minimum Path Sum Leetcode Solution	75
1318	Decode String Leetcode Solution	74
1319	Odd Even Linked List Leetcode Solution	73
1320	Binary Tree Inorder Traversal LeetCode Solution	72
1321	Shifting Letters LeetCode Solution	72
1322	Longest Common Subsequence LeetCode Solution	72
1323	Best Meeting Point LeetCode Solution	71
1324	Shortest Unsorted Continuous Subarray LeetCode Solution	71
1325	Maximum Population Year LeetCode Solution	71
1326	Find the Town Judge LeetCode Solution	70
1327	Find the Town Judge LeetCode Solution	70
1328	Sum Root to Leaf Numbers LeetCode Solution	70
1329	Design Add and Search Words Data Structure LeetCode Solution	68
1330	Maximum Population Year LeetCode Solution	66
1331	Rectangle Overlap LeetCode Solution	66
1332	Score of Parenthesis LeetCode Solution	65
1333	Flatten Binary Tree to Linked List LeetCode Solution	63
1334	Insert into a Sorted Circular Linked List LeetCode Solution	63
1335	Stone Game IV LeetCode Solution	62
1336	Is Graph Bipartite? LeetCode Solution	60
1337	Range Sum Query 2D – Immutable LeetCode Solution	60
1338	Valid Triangle Number LeetCode Solution	59
1339	Reveal Cards In Increasing Order Leetcode Solution	59
1340	Divide Chocolate LeetCode Solution	51
1341	Step-By-Step Directions From a Binary Tree Node to Another LeetCode Solution	46
1342	Range Sum of BST LeetCode Solution	44
1343	Reverse Integer Leetcode Solution	41
1344	Sort Colors LeetCode Solution	40
1345	Find K Closest Elements LeetCode Solution	38
1346	Excel Sheet Column Number LeetCode Solution	34
1347	Rotate String LeetCode Solution	34
1348	Maximum Side Length of a Square with Sum Less than or Equal to Threshold LeetCode Solution	33
1349	High Five LeetCode Solution	6
1350	H-Index Leetcode Solution	2