Peak Index in a Mountain Array LeetCode Solution

Difficulty Level Medium
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Problem Statement

Peak Index in a Mountain Array LeetCode Solution – An array arr a mountain if the following properties hold:

  • arr.length >= 3
  • There exists some i with 0 < i < arr.length - 1 such that:
    • arr[0] < arr[1] < ... < arr[i - 1] < arr[i]
    • arr[i] > arr[i + 1] > ... > arr[arr.length - 1]

Given a mountain array arr, return the index i such that arr[0] < arr[1] < ... < arr[i - 1] < arr[i] > arr[i + 1] > ... > arr[arr.length - 1].

You must solve it in O(log(arr.length)) time complexity.

Input: arr = [0,1,0]
Output: 1


The mountain increases until it doesn’t. The point at which it stops increasing is the peak.

Peak Index in a Mountain Array LeetCode SolutionPin

For this problem, we are trying to find a index where a[mid] > a[mid -1] AND a[mid] > a[mid + 1]. That is what the definition of a peak is.

We can use binary search to do this in O(log n) time, but before we go on we need to set up some ground rules on what values we will land on, and what do they mean.

There are four different scenarios we need to take into consideration

  • We land on the peak where a[mid] > a[mid – 1] and a[mid] > a[mid +1]
  • We land in a valley where a[mid] < a[mid-1] and a[mid] < a[mid + 1]
  • We land on a slope, and need to see which way is facing towards a peak (this point is the last two scenarios)

It’s also very important to point out that index 0 or index a.length – 1 can be a peak as well! So we need some custom logic in here for that.


Java Code for Peak Index in a Mountain Array:

class Solution {
    public int peakIndexInMountainArray(int[] arr) {
        int start = 0;
        int end = arr.length - 1;

        while (start < end) {
            int mid = start + (end - start) / 2;

                end = mid;
            }else if (arr[mid]<arr[mid+1]){
                start = mid+1;

        return start;

Python Code for Peak Index in a Mountain Array:

class Solution(object):
    def peakIndexInMountainArray(self, arr):
        start = 0
        end = len(arr)-1

        while start<=end:
            mid = (start+end)//2
            if start==end:
                return mid
            elif arr[mid] > arr[mid+1]:
                end = mid
                start = mid+1

Complexity Analysis for Peak Index in a Mountain Array LeetCode Solution

Time Complexity

O(logn), where N is the length of the Array as we are doing binary search.

Space Complexity

O(1), as we are not using any extra space.

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593Maximum path sum in a triangle173
5943Sum Closest LeetCode Solution173
595Shortest Path in a Grid with Obstacles Elimination LeetCode Solution173
596Maximum Number of Chocolates to be Distributed Equally Among k Students173
597Distance Between Bus Stops Leetcode Solution173
598Minimum number of distinct elements after removing m items172
599Stone Game LeetCode171
600Rotate Image LeetCode Solution171
601Find minimum difference between any two elements171
602Minimum insertions to form a palindrome with permutations allowed171
603Same Tree LeetCode Solution171
604Sieve of Eratosthenes171
605Sort Characters By Frequency LeetCode Solution171
606Replace Elements with Greatest Element on Right Side Leetcode Solution171
607Minimum number of subsets with distinct elements171
608How to check if two given sets are disjoint?171
609Permutation in String Leetcode Solution171
610Word Wrap Problem170
611Applications of Breadth First Search and Depth First Search170
612XOR Operation in an Array Leetcode Solution170
613Painting Fence Algorithm170
614Frog Jump Leetcode Solution170
615K Empty Slots LeetCode170
616Sort Array By Parity LeetCode Solution170
617Remove All Occurrences of a Substring LeetCode Solution170
618Find if an Expression has Duplicate Parenthesis or Not170
619Word Pattern170
620Smallest Good Base170
621Reverse a stack without using extra space in O(n)170
622Bubble sort using two Stacks170
623Tracking current Maximum Element in a Stack169
624Isomorphic Strings169
625Distance of nearest cell having 1 in a binary matrix169
626Best Time to Buy and Sell Stock LeetCode Solution169
627Minimum Depth of Binary Tree Leetcode Solution169
628Defanging an IP Address Leetcode Solution169
629Printing brackets in Matrix Chain Multiplication Problem169
630House Robber169
631Maximum Consecutive Numbers Present in an Array169
632License Key Formatting Leetcode Solution168
633Find Sum of all unique sub-array sum for a given array168
634Longest Increasing Subsequence168
635Segregate 0s and 1s in an Array168
636Non-overlapping sum of two sets168
637Minimum Cost to Hire K Workers168
638Longest Substring with At Most K Distinct Characters LeetCode Solution168
639Find the Duplicate Number LeetCode Solution168
640Wiggle Sort168
641Moving Average from Data Stream Leetcode Solution167
642Optimal Account Balancing LeetCode Solution167
643Binary Tree Zigzag Level Order Traversal LeetCode Solution167
644Find Maximum Level sum in Binary Tree167
645Count Good Nodes in Binary Tree Leetcode Solution167
646Coin Change Problem167
647Maximum difference between first and last indexes of an element in array167
648Sum of All Odd Length Subarrays Leetcode Solution167
649Valid Palindrome II Leetcode Solution167
650Iterative Method to find Height of Binary Tree167
651How to Create Mergable Stack?167
652Minimum Number of Steps to Make Two Strings Anagram Leetcode Solutions166
653GCD Of Two Numbers166
654Check If It Is a Straight Line Leetcode Solution166
655Queries for counts of array elements with values in given range166
656Kth Missing Positive Number Leetcode Solution166
657Strobogrammatic Number LeetCode Solution166
658Employee Free Time LeetCode Solution166
659Best Time to Buy and Sell Stock with Cooldown Leetcode Solution166
660Merge Two Balanced Binary Search Trees166
661Maximum Number of Occurrences of a Substring Leetcode Solution166
662Find the Distance Value Between Two Arrays Leetcode Solution165
663Find Largest d in Array such that a + b + c = d165
664Valid Palindrome165
665Flipping an Image LeetCode Solution165
666Letter Combinations of a Phone Number165
667Number of Provinces Leetcode Solution165
668Reorganize String165
669Path With Maximum Minimum Value LeetCode Solution165
670Convert an array to reduced form165
671Longest Substring with At Least K Repeating Characters LeetCode Solution165
672Delete consecutive same words in a sequence164
673Partition Labels LeetCode Solution164
674Maximum Number of Coins You Can Get Leetcode Solution164
675Find pairs with given sum such that elements of pair are in different rows164
676Populating Next Right Pointers in Each Node163
677Partition Array Into Three Parts With Equal Sum Leetcode Solution163
678Reducing Dishes LeetCode Solution163
679Power of Four Leetcode Solution163
680Longest Increasing Path in a Matrix LeetCode Solution163
681Print the Fibonacci numbers in reverse order163
682Number of Dice Rolls With Target Sum LeetCode Solution163
683Valid Perfect Square Leetcode Solution163
684Recover Binary Search Tree163
685K Empty Slots163
686Permutation Sequence LeetCode Solution163
687Rearrange an array in order – smallest, largest, 2nd smallest, 2nd largest163
688Edit Distance LeetCode Solution163
689Factorial Trailing Zeroes Leetcode Solution163
690Check If Two String Arrays are Equivalent Leetcode Solution163
691Inorder Successor of a node in Binary Tree163
692Sort Array by Increasing Frequency Leetcode Solution162
693Lucky Numbers in a Matrix Leetcode Solution162
694BFS vs DFS for Binary Tree162
695Check if a queue can be sorted into another queue using a stack162
696Merge Two Binary Trees LeetCode Solution162
697Construct BST from given Preorder Traversal162
698String to Integer (atoi) LeetCode Solution162
699Increasing Decreasing String Leetcode Solution162
700To Lower Case Leetcode Solution162
701Maximum Product of Two Elements in an Array Leetcode Solution162
702Form minimum number from given sequence162
703Dynamic Programming Basics162
704Remove Invalid Parentheses Leetcode Solution162
705Subset Sum Leetcode161
706Ugly Number Leetcode Solution161
707Convert a Number to Hexadecimal Leetcode Solution161
708Reversing a Queue using Recursion161
709Reverse Only Letters LeetCode Solution161
710Binary Tree zigzag level order Traversal161
711Robot Room Cleaner Leetcode Solution161
712Reservoir Sampling161
713Find the Smallest Divisor given a Threshold Leetcode Solution161
714Unique Paths II Leetcode Solution161
715Find whether an array is subset of another array161
716Keyboard Row Leetcode Solution160
717Restore IP Addresses Leetcode Solution160
718Majority Element II Leetcode Solution160
719Delete Nth node from the end of the given linked list160
720Binomial Coefficient160
721Find Leaves of Binary Tree LeetCode Solution160
722Perform String Shifts Leetcode159
723Numbers with prime frequencies greater than or equal to k159
724Bulb Switcher LeetCode Solution159
725Find the largest multiple of 3159
726Add and Search Word – Data structure design LeetCode159
727Decompress Run-Length Encoded List Leetcode Solution159
728Check if Two Expressions With Brackets are Same159
729Find the node with minimum value in a Binary Search Tree159
730Hamming Distance Leetcode Solution158
731Minimum Cost For Tickets Leetcode Solution158
732Sum of f(a[i], a[j]) over all pairs in an array of n integers158
733Find Pair with Greatest Product in Array158
734Race Car LeetCode Solution158
735Number of Islands II LeetCode Solution158
736Morris Traversal158
737Finding K closest element158
738Maximum 69 Number Leetcode Solution158
739Maximum Product of Three Numbers LeetCode Solution158
740Rank Transform of an Array Leetcode Solution157
741String Compression LeetCode Solution157
742Minimum Distance Between BST Nodes Leetcode Solution157
743Student Attendance Record I Leetcode Solution157
744Merge K Sorted Linked Lists157
745Diagonal Traversal of Binary Tree157
746Word Pattern LeetCode Solution157
747Generate all possible sorted arrays from alternate elements of two given sorted arrays157
748Find Maximum Depth of Nested Parenthesis in a String157
749Invert Binary Tree LeetCode Solution157
750Sorted Linked List to Balanced BST157
751First Unique Character in a String LeetCode Solution157
752Tiling Problem157
753Maximum Depth of N-ary Tree Leetcode Solution157
754Best Meeting Point LeetCode Solution156
755Minimum time required to rot all oranges156
756Largest subarray with equal number of 0s and 1s156
757Non-decreasing Array LeetCode Solution156
758Kth ancestor of a node in binary tree156
759Check If Array Pairs Are Divisible by k LeetCode Solution156
760Minimum Height Trees156
761Symmetric Tree Leetcode Solution156
762Find if Path Exists in Graph Leetcode Solution156
763Remove brackets from an algebraic string containing + and – operators156
764Queue based approach for first non-repeating character in a stream156
765Longest Span with same Sum in two Binary arrays156
766Special Array With X Elements Greater Than or Equal X Leetcode Solution156
767Find All Duplicates in an Array LeetCode Solution156
768Find unique character in a string156
769Remove Nth Node From End of List Leetcode Solution156
770Binary Tree Maximum Path Sum LeetCode Solution156
771Partition to K Equal Sum Subsets Leetcode Solution155
772Minimize Maximum Pair Sum in Array LeetCode Solution155
773Final Prices With a Special Discount in a Shop Leetcode Solution155
774Snakes and Ladders LeetCode Solution155
775Find Median from Data Stream LeetCode Solution155
776Largest rectangular sub-matrix whose sum is 0155
777Elements to be added so that all elements of a range are present in array155
778Largest Rectangle in Histogram LeetCode Solution155
779Maximum Length of a Concatenated String with Unique Characters Leetcode Solution155
780Search a 2D Matrix II Leetcode Solution155
781Stack Permutations (Check if an array is stack permutation of other)155
782Evaluate Reverse Polish Notation LeetCode Solution155
783Jump Game155
784Valid Number154
785Count items common to both the lists but with different prices154
786Transpose Graph154
787Total Numbers With no Repeated Digits in a Range154
788Split a String in Balanced Strings Leetcode Solution154
789k-th missing element in increasing sequence which is not present in a given sequence154
790Maximum Difference Between Increasing Elements LeetCode Solution154
791Program for Bridge and Torch problem154
792Linked List Cycle154
793Interval Tree153
794Print a Binary Tree in Vertical Order153
795Minimum Jumps to Reach Home LeetCode Solution153
796Get Maximum in Generated Array Leetcode Solution153
797Sort an array according to the order defined by another array153
798Nearest Exit from Entrance in Maze LeetCode Solution153
799Search in a Binary Search Tree Leetcode Solution153
800One Edit Distance LeetCode Solution153
801Deletion in a Binary Tree153
802Base 7 Leetcode Solution153
803Growable array based stack153
804Last Stone Weight II LeetCode Solution153
805Count quadruples from four sorted arrays whose sum is equal to a given value x153
806N-Queens LeetCode Solution153
807Number of NGEs to the Right153
808Minimum number of jumps to reach end152
809Crawler Log Folder Leetcode Solution152
810A Space Optimized DP solution for 0-1 Knapsack Problem152
811Number Complement Leetcode Solution152
812Merge Sorted Array LeetCode Solution152
813Priority Queue using doubly linked list152
814Relative Ranks Leetcode Solution152
815Check for Palindrome after every character replacement Query152
816Iterative Preorder Traversal152
817Circular Queue152
818Subarray Product Less Than K LeetCode Solution152
819String comparison containing wildcards152
820Minimum swaps to make sequences increasing152
821Reorder Data in Log Files LeetCode Solution152
822Course Schedule II – LeetCode152
823Minimum Time Visiting All Points Leetcode Solution152
824Remove Duplicates from Sorted List LeetCode Solution152
825Maximum Profit in Job Scheduling Leetcode Solution152
826Remove Duplicates from Sorted List II152
827Nested List Weight Sum II LeetCode Solution152
828Maximum size subarray sum equals k151
829Form Minimum Number From Given Sequence151
830Spiral Matrix II Leetcode Solution151
831Sort Array By Parity II Leetcode Solution151
832Find all triplets with zero sum151
833Longest Subarray Having Count of 1s One More than Count of 0s151
834Make Two Arrays Equal by Reversing Sub-arrays Leetcode Solution150
835Insert into a Binary Search Tree Leetcode Solution150
836Can Place Flowers LeetCode Solution150
837Valid Parentheses Leetcode Solution150
838Given an Array of Pairs Find all Symmetric Pairs in it150
839Path with maximum average value150
840Alien Dictionary LeetCode Solution150
841Find the subarray with least average150
842Sum of nearest smaller and greater number150
843Regular Expression Matching150
844Convert BST to Min Heap150
845Brick Wall LeetCode Solution150
846Maximum Nesting Depth of the Parentheses Leetcode Solution150
847Friends Pairing Problem149
848Check whether a given Binary Tree is Complete or not149
849Sort Colors149
850Clone Graph LeetCode Solution149
851Check if a given array can represent Preorder Traversal of Binary Search Tree149
852Permutation Coefficient149
853Level order Traversal in Spiral Form149
854Minimum Number of Taps to Open to Water a Garden LeetCode Solution149
855Partition List Leetcode Solution149
856Count Distinct Elements in Every Window of Size K149
857Count Negative Numbers in a Sorted Matrix LeetCode Solution149
858Find All Possible Recipes from Given Supplies LeetCode Solution149
859Subset with sum divisible by m149
860Subsequence of Size K With the Largest Even Sum LeetCode Solution149
861Top K Frequent Words LeetCode Solution149
862Binary Search Tree Search and Insertion149
863Design a Stack With Increment Operation Leetcode Solution148
864Find Maximum Sum Possible Equal Sum of Three Stacks148
865Range LCM Queries148
866Check if stack elements are pairwise consecutive148
867Tree Traversal (Preorder, Inorder & Postorder)148
868LCS (Longest Common Subsequence) of three strings148
869Sequences of given length where every element is more than or equal to twice of previous148
870An Interesting Method to generate Binary Numbers from 1 to n148
871Matrix Chain Multiplication148
872Guess Number Higher or Lower LeetCode Solution148
873Missing Element in Sorted Array LeetCode Solution148
874Find the Only Repetitive Element Between 1 to N-1148
875Minimum Sum Path in a Triangle148
876Identify and Mark Unmatched Parenthesis in an Expression147
877Water Bottles Leetcode Solution147
878Distinct adjacent elements in an array147
879Best Time to Buy and Sell Stock with Transaction Fee Leetcode Solution147
880Repeated Substring Pattern LeetCode Solution147
881Balanced Expression with Replacement147
882Diagonal Traverse LeetCode Solution147
883Convert Sorted List to Binary Search Tree147
884K’th Largest Element in BST when modification to BST is not allowed147
885Design Browser History LeetCode Solution147
886Sorted Array to Balanced BST147
887Brightest Position on Street LeetCode Solution147
888Diagonal Traversal LeetCode Solution147
889Number of Days Between Two Dates LeetCode Solution147
890Guess Number Higher or Lower II146
891Rearrange an Array Such that arr[i] is equal to i146
892Three way partitioning of an array around a given range146
893Time Based Key-Value Store LeetCode Solution146
894Union and Intersection of two Linked Lists146
895Minimum sum of multiplications of n numbers146
896GCDs of given index ranges in an array146
897Daily Temperatures Leetcode Solution146
898Special Positions in a Binary Matrix Leetcode Solution146
899Insert Delete GetRandom146
900Shortest Word Distance Leetcode Solution146
901BFS for Disconnected Graph146
902Destination City Leetcode Solution146
903Maximum Score After Splitting a String Leetcode Solution146
904Check if an Array is Stack Sortable146
905Count ways to reach the nth stair using step 1, 2 or 3145
906Minimum Swaps to Make Strings Equal Leetcode Solution145
907Rearrange Array such that arr[i] >= arr[j] if i is even and arr[i] <= arr[j] if i is odd and j < i145
908Lemonade Change Leetcode Solution145
909Delete And Earn145
910Least Number of Unique Integers after K Removals Leetcode Solution145
911Range sum queries without updates145
912Find distance between two nodes of a Binary Tree145
913Check if the given array can represent Level Order Traversal of Binary Search Tree145
914Spiral Matrix III LeetCode Solution145
915Find Common Characters Leetcode Solution145
916Robot Bounded In Circle LeetCode Solution145
917Palindrome Partitioning Leetcode Solution144
918Rearrange Spaces Between Words Leetcode Solution144
919Construct BST from its given Level Order Traversal144
920Print Fibonacci sequence using 2 variables144
921Merge Two Sorted Lists Leetcode144
922Queue using Stacks144
923Number of Distinct Islands Leetcode Solution144
924Vertical sum in a given binary tree144
926Construct Complete Binary Tree from its Linked List Representation144
927Minimum Height Trees LeetCode Solution143
928Maximum Frequency Stack Leetcode Solution143
929Stone Game II Leetcode143
930Alien Dictionary143
9313 Sum143
932Check if any two intervals overlap among a given set of intervals143
933Maximum Subarray Sum Excluding Certain Elements143
934Construct the Rectangle Leetcode Solution143
935A program to check if a binary tree is BST or not143
936Split Array Into Consecutive Subsequences143
937Averages of Levels in Binary Tree143
938Difference Array | Range update query in O(1)142
939Lexicographical Numbers Leetcode Solution142
940Largest area rectangular sub-matrix with equal number of 1’s and 0’s142
941Count Subarrays with Same Even and Odd Elements142
942Strongly Connected Component142
943Queries for GCD of all numbers of an array except elements in a given range142
944Iterative Postorder Traversal Using Two Stacks142
945Create Maximum Number142
946Set Matrix Zeroes Leetcode Solution142
947Binary Tree Longest Consecutive Sequence LeetCode Solution142
948Trim a Binary Search Tree142
949Infix to Postfix142
950Remove Duplicates from Sorted List II LeetCode Solution142
951Longest Palindromic Subsequence142
952Unique Paths II141
953Binary array after M range toggle operations141
954Number of Equivalent Domino Pairs Leetcode Solution141
955Shuffle 2n integers as without using extra space141
956Analyze User Website Visit Pattern LeetCode Solution141
957Find all permuted rows of a given row in a matrix141
958All Unique Triplets that Sum up to a Given Value141
959Sliding Window Maximum141
960Collect maximum points in a grid using two traversals141
961Count Submatrices With All Ones LeetCode Solution141
962Three Consecutive Odds Leetcode Solution140
963Can Make Arithmetic Progression From Sequence Leetcode Solution140
964Dividing Array into Pairs With Sum Divisible by K140
965Minesweeper LeetCode Solution140
966Height of a generic tree from parent array140
967Pattern Occurrences using Stack140
968Merging Intervals140
969Word Break140
970Count subarrays where second highest lie before highest140
971Maximum Product Subarray140
972Intersection of Two Linked Lists LeetCode Solution140
973Reverse Nodes in K-Group140
974Find postorder traversal of BST from preorder traversal140
975Sign of the Product of an Array LeetCode Solution140
976Palindrome Partitioning139
977Find the Difference Leetcode Solution139
978Count Primes in Ranges139
979Newman-Conway Sequence139
980Length of Longest Fibonacci Subsequence139
981The Painter’s Partition Problem139
982Count pair with Given Sum139
983Kth Smallest Element in a BST Leetcode Solution139
984Median of Two Sorted Arrays139
985Product of Array Except Self LeetCode Solution139
986Binary Search Tree Delete Operation139
987Longest Nice Substring LeetCode Solution139
988Level Order Traversal of Binary Tree139
989Symmetric Tree139
990Asteroid Collision LeetCode Solution138
991Segment Tree138
992Find Maximum of Minimum for Every Window Size in a Given Array138
993My Calendar I LeetCode Solution138
994Maximize Sum of Array after K Negations Leetcode Solution138
995K Closest Points to Origin Leetcode Solution138
996Check If a Word Occurs As a Prefix of Any Word in a Sentence Leetcode Solution138
997Climbing stairs138
998Find Duplicate Subtrees137
999Number Of Longest Increasing Subsequence137
1000Merge Sort137
1001Maximum subsequence sum such that no three are consecutive137
1002Double the first element and move zero to end137
1003String Matching in an Array Leetcode Solution137
1004The Maze III LeetCode Solution137
1005Valid Boomerang Leetcode Solution137
1006Largest Number Leetcode Solution137
1007Maximum Product of Indexes of Next Greater on Left and Right137
1008Construction of Longest Increasing Subsequence (N log N)137
1009Compute nCr % p137
1010Breadth First Search (BFS) for a Graph137
1011Depth First Search (DFS) for a Graph137
1012Find the First Circular Tour that visits all the Petrol Pumps137
1013Number of palindromic paths in a matrix137
1014Friends Of Appropriate Ages LeetCode Solution137
1015Largest divisible pairs subset137
1016Maximum Length of Repeated Subarray137
1017Boundary Traversal of binary tree137
1018Shortest Completing Word Leetcode Solution137
1019Morris Inorder Traversal136
1020Serialize and Deserialize Binary Tree136
1021Minimum Index Sum of Two Lists136
1022Graph Valid Tree LeetCode Solution136
1023Next Greater Element III LeetCode Solution136
1024Level order traversal using two Queues136
1025Insertion in a Binary Tree136
1026Largest Substring Between Two Equal Characters Leetcode Solution136
1027Construct Binary Tree from given Parent Array representation136
1028Kill Process LeetCode Solution136
1029Binary Search Tree136
1030Rearrange an array such that ‘arr[j]’ becomes ‘i’ if ‘arr[i]’ is ‘j’136
1031First missing positive136
1032Partition Equal Subset Sum136
1033Maximum Number of Ways to Partition an Array LeetCode Solution136
1034Boolean Parenthesization Problem136
1035Find number of pairs in an array such that their XOR is 0136
1036Maximum weight transformation of a given string136
1037Make The String Great Leetcode Solution136
1038Longest subsequence such that difference between adjacents is one135
1039Design Hit Counter LeetCode Solution135
1040Scramble String LeetCode Solution135
1041Count minimum steps to get the given desired array135
1042Invalid Transactions LeetCode Solution135
1043Advantages of BST over Hash Table135
1044K maximum sums of overlapping contiguous sub-arrays135
1045Build an Array With Stack Operations Leetcode Solution135
1046Decrypt String from Alphabet to Integer Mapping Leetcode Solution135
1047Rearrange array such that even positioned are greater than odd134
1048Path Sum II LeetCode Solution134
1049Available Captures for Rook Leetcode Solution134
1050Ugly Numbers134
1051Balanced Binary Tree134
1052Maximum Sum of 3 Non-Overlapping Subarrays134
1053Custom Sort String Leetcode Solution134
1054Validate Binary Search Tree134
1055Iterative Depth First Traversal of Graph133
1056Defanging an IP Address LeetCode Solution133
1057Super Ugly Number133
1058Implement Trie (Prefix Tree) Leetcode Solution133
1059Bitwise AND of Numbers Range LeetCode Solution133
1060Maximum length subsequence with difference between adjacent elements as either 0 or 1133
1061Ugly Number II LeetCode Solution133
1062Employee Importance LeetCode Solution133
1063Count pairs from two sorted arrays whose sum is equal to a given value x133
1064Kth Smallest Element in a Sorted Matrix LeetCode Solution133
1065Add two numbers133
1066Maximum difference between frequency of two elements such that element having greater frequency is also greater133
1067Lowest Common Ancestor132
1068Populating Next Right Pointers in Each Node Leetcode Solution132
1069Find Peak Element132
1070Recover Binary Search Tree Leetcode Solution132
1071Remove Duplicates from Sorted Array II Leetcode Solution132
1072Move all negative elements to end in order with extra space allowed132
1073Generate Parentheses Leetcode Solution132
1074Regular Expression Matching Regular Expression Matching LeetCode Solution132
1075Search in Sorted Rotated Array132
1076Largest BST Subtree LeetCode Solution131
1077Find a Peak Element II LeetCode Solution131
1078Number of Students Doing Homework at a Given Time Leetcode Solution131
1079Subarrays with K Different Integers Leetcode Solution131
1080Longest Bitonic Subsequence131
1081Binary Tree Right Side View LeetCode Solution131
1082Determine Whether Matrix Can Be Obtained By Rotation LeetCode Solution131
1083Root to Leaf path with target sum Leetcode Solutions131
1084Maximize Distance to Closest Person LeetCode Solution130
1085Clone a Binary Tree with Random Pointers130
1086Day of the Year Leetcode Solution130
1087Number of siblings of a given Node in n-ary Tree130
1088Minimum Size Subarray Sum130
1089Find whether a subarray is in form of a mountain or not130
1090Rearrange array such that even index elements are smaller and odd index elements are greater130
1091Kth Smallest Product of Two Sorted Arrays LeetCode Solution130
1092Number of Closed Islands Leetcode Solution130
1093Smallest Common Region Leetcode Solution130
1094Combination Sum IV LeetCode Solution130
1095Remove Palindromic Subsequences Leetcode Solution129
1096Consecutive Characters LeetCode Solution129
1097Increasing Triplet Subsequence LeetCode Solution129
1098Minimum Absolute Difference in BST Leetcode Solution129
1099Serialize and Deserialize Binary Tree LeetCode Solution129
1100Next Permutation Leetcode Solution129
1101Find maximum difference between nearest left and right smaller elements129
1102Convert BST into a Min-Heap without using array129
1103Level of Each node in a Tree from source node129
1104Count Largest Group Leetcode Solution129
1105Types of Binary Tree129
1106Find the minimum distance between two numbers129
1107Distinct Subsequences129
1108Find Smallest Range Containing Elements from k Lists129
1109Binary Tree Data Structure129
1110Remove duplicates from sorted array128
1111Third Maximum Number Leetcode Solution128
1112Iterative method to find ancestors of a given binary tree128
1113Valid Tic-Tac-Toe State LeetCode Solution128
1114Path Sum128
1115Cutting a Rod128
1116Print all triplets in sorted array that form AP128
1117Find Three Element From Different Three Arrays Such That a + b + c = sum128
1118Construct Binary Tree from Preorder and Postorder Traversal LeetCode Solution128
1119Constant time range add operation on an array128
1120Divisible Pairs Counting128
1121Prime Palindrome LeetCode Solution127
1122Palindrome Permutation LeetCode Solution127
1123Reformat The String Leetcode Solution127
1124Sum of Even Numbers After Queries127
1125Print Next Greater Number of Q queries127
1126Products of ranges in an array127
1127Longest Subarray of 1’s After Deleting One Element LeetCode Solution127
1128Maximum Product Subarray127
1129Print Right View of a Binary Tree126
1130Search Insert Position126
1131Minimum Score Triangulation of Polygon Leetcode Solution126
1132Thousand Separator Leetcode Solution126
1133Cells with Odd Values in a Matrix LeetCode Solution126
1134Delete Nodes and Return Forest Leetcode Solution126
1135Bottom View of a Binary Tree126
1136Mean of Array After Removing Some Elements Leetcode Solution126
1137Longest Increasing Consecutive Subsequence126
1138Write Code to Determine if Two Trees are Identical126
1139Topological Sorting125
1140Search an Element in Sorted Rotated Array125
1141Minimum sum of squares of character counts in a given string after removing k characters125
1142Palindromic Substrings Leetcode Solution125
1143Construct K Palindrome Strings LeetCode Solution125
1144Merge two BSTs with limited extra space125
1145Moser-de Bruijn Sequence125
1146Swap Nodes In Pairs124
1147Priority Queue124
1148Maximum Binary Tree124
1149Subset Sum Problem in O(sum) space124
1150Closest Binary Search Tree Value Leetcode Solution124
1151Maximum Product of Splitted Binary Tree LeetCode Solution124
1152Find Two Non-overlapping Sub-arrays Each With Target Sum LeetCode Solution124
1153Red-Black Tree Introduction124
1154Find maximum length Snake sequence124
1155Check Array Formation Through Concatenation Leetcode Solution123
1156Print modified array after executing the commands of addition and subtraction123
1157Bus Routes Leetcode Solution123
1158Golomb sequence123
1159Diameter of N-Ary Tree LeetCode Solution123
1160Possible Bipartition LeetCode Solution123
1161Transform a BST to Greater sum Tree122
1162Kth Smallest Number in Multiplication Table Leetcode Solution122
1163Maximize sum of consecutive differences in a circular array122
1164Binary Tree to Binary Search Tree Conversion122
1165Web Crawler LeetCode Solution122
1166Find Largest Value in Each Tree Row LeetCode Solution122
1167Rotate Array122
1168Minimum Sideway Jumps LeetCode Solution122
1169Search Suggestions System LeetCode Solution122
1170Find a sorted subsequence of size 3 in linear time122
1171Queries for Number of Distinct Elements in a Subarray122
1172Remove Max Number of Edges to Keep Graph Fully Traversable Leetcode Solution122
1173Compare Strings by Frequency of the Smallest Character Leetcode Solution121
1174Decision Tree121
1175Count even length binary sequences with same sum of first and second half bits121
1176Graph and its representation121
1177Minimum Cost to Move Chips to The Same Position LeetCode Solution121
1178Matchsticks to Square Leetcode Solution121
1179Longest Repeated Subsequence121
1180Find the smallest binary digit multiple of given number121
1181Contiguous Array LeetCode Solution120
1182Lowest Common Ancestor in Binary Search Tree120
1183Factorial Trailing Zeroes LeetCode Solution120
1184Convert Sorted Array to Binary Search Tree LeetCode Solutions120
1185First Bad Version120
1186Swapping Nodes in a Linked List Leetcode Solution120
1187Sum of Left Leaves LeetCode Solution119
1188K’th Largest element in BST using constant extra space119
1189Maximum sum bitonic subarray119
1190Number of Orders in the Backlog Leetcode Solution119
1191Decrease Elements To Make Array Zigzag LeetCode Solution119
1192Reverse a Path in BST using Queue119
1193Queue Reconstruction by Height119
1194Valid Triangle Number119
1195Minimum Moves to Equal Array Elements LeetCode Solution119
1196Maximum number of segments of lengths a, b and c118
1197How to print maximum number of A’s using given four keys118
1198Reformat Date LeetCode Solution118
1199Maximum sum of pairs with specific difference118
1200Count Pairs Whose Products Exist in Array118
1201Lowest Common Ancestor of a Binary Tree Leetcode Solution118
1202Given a binary tree, how do you remove all the half nodes?118
1203Closest Leaf in a Binary Tree LeetCode Solution118
1204Range Queries for Longest Correct Bracket Subsequence118
1205Moving Stones Until Consecutive Leetcode Solution118
1206Array Queries for multiply replacements and product117
1207Kth Smallest Element in a BST117
1208Guess The Word117
1209Champagne Tower LeetCode Solution117
1210Path Crossing Leetcode Solution116
1211Replace two consecutive equal values with one greater116
1212Concatenation of Array LeetCode Solution116
1213Filter Restaurants by Vegan-Friendly, Price and Distance Leetcode Solution116
1214Minimum Swaps To Make Sequences Increasing LeetCode Solution116
1215Convert Integer to the Sum of Two No-Zero Integers Leetcode Solution116
1216Valid Perfect Square LeetCode Solution115
1217Range Sum Query using Sparse Table115
1218Integer Break LeetCode Solution115
1219Arithmetic Slices II – Subsequence LeetCode Solution115
1220Flatten 2D Vector LeetCode Solution115
1221Perfect Squares LeetCode Solution115
1222Write a function to get the intersection point of two Linked Lists115
1223Maximum sum of a path in a Right Number Triangle114
1224Maximum Depth Of Binary Tree114
1225BST to a Tree with Sum of all Smaller Keys114
1226Check if each internal node of a BST has exactly one child114
1227Power of Two114
1228New 21 Game114
1229Design Skiplist LeetCode Solution114
1230Check Completeness of a Binary Tree LeetCode Solution114
1231Divide Two Integers Leetcode Solution114
1232Sliding Window Median Leetcode Solution114
1233The kth Factor of n Leetcode Solution114
1234LRU Cache Leetcode Solution114
1235Mean of range in array114
1236Largest Plus Sign Leetcode Solution113
1237Queries on Probability of Even or Odd Number in given Ranges113
1238Maximum Value at a Given Index in a Bounded Array LeetCode Solution113
1239Maximize Elements Using Another Array113
1240Contiguous Array113
1241Print modified array after multiple array range increment operations113
1242Longest Common Prefix Using Word by Word Matching113
1243Check if all levels of two Binary Tree are anagrams or not113
1244Check for Identical BSTs without building the trees113
1245Bold Words in String LeetCode Solution113
1246Find Minimum in Rotated Sorted Array II LeetCode Solution113
1247Parallel Courses II LeetCode Solution112
1248Print Ancestors of a Given Binary Tree Node Without Recursion112
1249Print n terms of Newman-Conway Sequence112
1250Maximum Array from Two given Arrays Keeping Order Same112
1251Find k-th smallest element in BST (Order Statistics in BST)112
1252Count Subsets Having Distinct Even Numbers111
1253Graph Cloning111
1254Find minimum number of merge operations to make an array palindrome111
1255Merge k Sorted Lists Leetcode Solution111
1256Symmetric Tree LeetCode Solution Leetcode Solution111
1257Maximum Product Subarray111
1258Missing Number110
1259Smallest Range II Leetcode Solution110
1260Count and Toggle Queries on a Binary Array110
1261Check if two nodes are on the same path in a Tree110
1262Minimum Remove to Make Valid Parentheses LeetCode Solution110
1263Verify Preorder Serialization of a Binary Tree109
1264Number of elements less than or equal to a given number in a given subarray109
1265Next greater element109
1266Image Overlap LeetCode Solution108
1267Excel Sheet Column Title LeetCode Solution108
1268Minimum Time to Collect All Apples in a Tree LeetCode Solution108
1269Check If a String Can Break Another String Leetcode Solution108
1270Orderly Queue LeetCode Solution107
1271Palindrome Partitioning107
1272Min Cost Climbing Stairs LeetCode Solution107
1273Different Ways to Add Parentheses Leetcode Solution107
1274Koko Eating Bananas LeetCode Solution107
1275Peeking Iterator LeetCode Solution105
1276Check if X can give change to every person in the Queue105
1277Newman–Shanks–Williams prime105
1278Longest Substring Without Repeating Characters Leetcode Solution105
1279Largest Submatrix With Rearrangements LeetCode Solution105
1280Check in binary array the number represented by a subarray is odd or even104
1281Merge Sorted Array103
1282Range Minimum Query (Square Root Decomposition and Sparse Table)103
1283Array Nesting Leetcode Solution102
1284Arranging Coins Leetcode Solution101
1285Maximum Sum Increasing Subsequence101
1286Find maximum average subarray of k length100
1287Encoded String With Shortest Length LeetCode Solution100
1288Maximum product of an increasing subsequence100
1289Number of indexes with equal elements in given range99
1290Queries for Decimal Values of Subarrays of a Binary Array99
1291Minimum Total Space Wasted With K Resizing Operations LeetCode Solution99
1292Minimum Number of People to Teach LeetCode Solution98
1293Convert to Base -2 LeetCode Solution98
1294Reach a Number LeetCode Solution97
1295Convert a BST to a Binary Tree such that sum of all greater keys is added to every key97
1296Random Pick Index LeetCode Solution97
1297Add Two Numbers II Leetcode Solution96
1298Check given array of size n can represent BST of n levels or not96
1299Vertical Order Traversal of Binary Tree LeetCode Solution96
1300Find the Winner of the Circular Game LeetCode Solution96
1301Binary Tree to Binary Search Tree Conversion using STL set96
1302Continuous Subarray Sum LeetCode Solution96
1303Palindrome Number LeetCode Solution95
1304Queries on XOR of greatest odd divisor of the range95
1305Number of Subsequences That Satisfy the Given Sum Condition LeetCode solution95
1306Jump Game IV LeetCode Solution95
1307Insert Delete GetRandom O(1) Leetcode Solution94
1308Minimum Possible Integer After at Most K Adjacent Swaps On Digits LeetCode Solution94
1309Design Underground System Leetcode Solution90
1310Print Maximum Length Chain of Pairs89
1311Detect Capital Leetcode Solution87
1312Design A Leaderboard Leetcode Solution86
1313Top K Frequent Elements LeetCode Solution83
1314Minimum Swaps to Group All 1’s Together Leetcode Solution83
1315Substring with Concatenation of All Words Leetcode Solution83
1316Binary Tree Inorder Traversal LeetCode Solution81
1317Minimum Path Sum Leetcode Solution80
1318Count Sub Islands LeetCode Solution80
1319Shifting Letters LeetCode Solution79
1320Longest Common Subsequence LeetCode Solution77
1321Odd Even Linked List Leetcode Solution77
1322Find the Town Judge LeetCode Solution76
1323Best Meeting Point LeetCode Solution76
1324Decode String Leetcode Solution76
1325Find the Town Judge LeetCode Solution75
1326Maximum Population Year LeetCode Solution75
1327Shortest Unsorted Continuous Subarray LeetCode Solution72
1328Sum Root to Leaf Numbers LeetCode Solution72
1329Rectangle Overlap LeetCode Solution71
1330Maximum Population Year LeetCode Solution71
1331Design Add and Search Words Data Structure LeetCode Solution70
1332Score of Parenthesis LeetCode Solution67
1333Flatten Binary Tree to Linked List LeetCode Solution67
1334Stone Game IV LeetCode Solution67
1335Range Sum Query 2D – Immutable LeetCode Solution66
1336Insert into a Sorted Circular Linked List LeetCode Solution66
1337Reveal Cards In Increasing Order Leetcode Solution63
1338Valid Triangle Number LeetCode Solution62
1339Is Graph Bipartite? LeetCode Solution62
1340Divide Chocolate LeetCode Solution55
1341Step-By-Step Directions From a Binary Tree Node to Another LeetCode Solution48
1342Reverse Integer Leetcode Solution46
1343Range Sum of BST LeetCode Solution45
1344Sort Colors LeetCode Solution42
1345Find K Closest Elements LeetCode Solution40
1346Maximum Side Length of a Square with Sum Less than or Equal to Threshold LeetCode Solution38
1347Excel Sheet Column Number LeetCode Solution37
1348Rotate String LeetCode Solution37
1349H-Index Leetcode Solution20
1350Maximum Size Subarray Sum Equals k Leetcode Solution20
1351High Five LeetCode Solution19
1352Insert Delete GetRandom O(1) – Duplicates allowed LeetCode Solution10
1353Unique Binary Search Trees LeetCode Solution10
1354Monotonic Array Leetcode Solution10
1355Valid Triangle Number LeetCode Solution7
1356Swim in Rising Water LeetCode Solution6
1357Peak Index in a Mountain Array LeetCode Solution
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