Isomorphic Strings LeetCode Solution

Difficulty Level Easy
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Problem Statement

Isomorphic Strings LeetCode Solution – Given two strings s and tdetermine if they are isomorphic.

Two strings s and t are isomorphic if the characters in s can be replaced to get t.

All occurrences of a character must be replaced with another character while preserving the order of characters. No two characters may map to the same character, but a character may map to itself.

Isomorphic Strings LeetCode Solution

Input: s = "egg", t = "add"
Output: true

Explanation

The key-value pairs in the dictionary are the correspondence of the letter of the first word to the letter of the second word.

For example:

a = ‘title’, b = ‘paper’
In dict:
“t” : “p”
“i” : “a”
“l” : “e”
“e” : “r”

During the loop, we check if the letter has occurred to us before, and if so, we check if it “equals” the same letter from the second word as before.

After the loop, we check that the different keys do not correspond to the same value (that is, that different letters from the first word do not equal the same letter from the second one).

  1. We define a dictionary mapping_s_t which will be used to map characters in the string s to characters in the string t and another dictionary mapping_t_s which will be used to map characters in the string t to characters in the string s.
  2. Next, we iterate over the two strings one character at a time.
  3. Let’s assume the character in the first string is c1 and the corresponding character in the second string is c2.
    1. If c1 does not have a mapping in mapping_s_t and c2 does not have a mapping in mapping_t_s, we add the corresponding mappings in both dictionaries and move on to the next character.
    2. At this point, we expect both the character mappings to exist in the dictionaries and their values should be mapping_s_t[c1] = c2 and mapping_t_s[c2] = c1. If either of these conditions fails (c1 is not in the dictionary, c2 is not in the dictionary, unexpected mapping), we return false.
  4. Return true once both the strings have been exhausted.

Code

Java Code For Isomorphic Strings

class Solution {
    public boolean isIsomorphic(String s, String t) {
        
        int[] mappingDictStoT = new int[256];
        Arrays.fill(mappingDictStoT, -1);
        
        int[] mappingDictTtoS = new int[256];
        Arrays.fill(mappingDictTtoS, -1);
        
        for (int i = 0; i < s.length(); ++i) {
            char c1 = s.charAt(i);
            char c2 = t.charAt(i);
            
            // Case 1: No mapping exists in either of the dictionaries
            if (mappingDictStoT[c1] == -1 && mappingDictTtoS[c2] == -1) {
                mappingDictStoT[c1] = c2;
                mappingDictTtoS[c2] = c1;
            }
            
            // Case 2: Ether mapping doesn't exist in one of the dictionaries or Mapping exists and
            // it doesn't match in either of the dictionaries or both 
            else if (!(mappingDictStoT[c1] == c2 && mappingDictTtoS[c2] == c1)) {
                return false;
            }
        }
        
        return true;
    }
}

Python Code For Isomorphic Strings

class Solution:
    def isIsomorphic(self, s: str, t: str) -> bool:
        
        mapping_s_t = {}
        mapping_t_s = {}
        
        for c1, c2 in zip(s, t):
            
            # Case 1: No mapping exists in either of the dictionaries
            if (c1 not in mapping_s_t) and (c2 not in mapping_t_s):
                mapping_s_t[c1] = c2
                mapping_t_s[c2] = c1
            
            # Case 2: Ether mapping doesn't exist in one of the dictionaries or Mapping exists and
            # it doesn't match in either of the dictionaries or both            
            elif mapping_s_t.get(c1) != c2 or mapping_t_s.get(c2) != c1:
                return False
            
        return True

Complexity Analysis for Isomorphic Strings LeetCode Solution

Time Complexity

O(N)

Space Complexity

O(1)

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560Valid Anagrams177
561Assign Cookies Leetcode Solution177
562Find Words That Can Be Formed by Characters Leetcode Solution177
563Build Array From Permutation Leetcode Solution177
564Gold Mine Problem177
565Largest Perimeter Triangle Leetcode Solution177
566Integer to Roman177
567Minimum Operations to convert X to Y177
568Valid Sudoku177
569Convert Sorted Array to Binary Search Tree Leetcode Solution177
570Sum of Left Leaves Leetcode Solutions177
571Combinations Leetcode Solution176
572Shuffle an Array176
573Unique Binary Search Trees176
574Remove Linked List Elements Leetcode Solution176
57501 Matrix LeetCode Solution176
576Arrange given numbers to form the biggest number176
577Minimum Knight Moves LeetCode Solution176
578Island Perimeter Leetcode Solution176
579Hamming Distance176
580The Knapsack Problem175
581Rotate List Leetcode Solution175
582Summary Ranges Leetcode Solution175
583Trapping Rain Water LeetCode Solution175
584Count all subsequences having product less than K175
585Minimum Delete Operations to make all Elements of Array Same175
586Count the number of nodes at given level in a tree using BFS174
587LRU Cache LeetCode Solution174
588Decode Ways174
589Maximum sum rectangle in a 2D matrix174
590Find the smallest positive integer value that cannot be represented as sum of any subset of a given array173
591Distance Between Bus Stops Leetcode Solution173
592Maximum Distance in Array173
593Maximum path sum in a triangle173
594Maximum Number of Chocolates to be Distributed Equally Among k Students173
5953Sum Closest LeetCode Solution173
596Insert Interval Leetcode Solution173
597Shortest Path in a Grid with Obstacles Elimination LeetCode Solution173
598Minimum number of distinct elements after removing m items172
599Stone Game LeetCode171
600Replace Elements with Greatest Element on Right Side Leetcode Solution171
601Find minimum difference between any two elements171
602Sort Characters By Frequency LeetCode Solution171
603Sieve of Eratosthenes171
604Same Tree LeetCode Solution171
605How to check if two given sets are disjoint?171
606Minimum insertions to form a palindrome with permutations allowed171
607Permutation in String Leetcode Solution171
608Rotate Image LeetCode Solution171
609Minimum number of subsets with distinct elements171
610Applications of Breadth First Search and Depth First Search170
611Sort Array By Parity LeetCode Solution170
612XOR Operation in an Array Leetcode Solution170
613Frog Jump Leetcode Solution170
614Smallest Good Base170
615Remove All Occurrences of a Substring LeetCode Solution170
616Word Pattern170
617Painting Fence Algorithm170
618Find if an Expression has Duplicate Parenthesis or Not170
619Reverse a stack without using extra space in O(n)170
620Bubble sort using two Stacks170
621K Empty Slots LeetCode170
622Word Wrap Problem170
623Distance of nearest cell having 1 in a binary matrix169
624Tracking current Maximum Element in a Stack169
625Non-overlapping sum of two sets169
626Maximum Consecutive Numbers Present in an Array169
627Best Time to Buy and Sell Stock LeetCode Solution169
628Defanging an IP Address Leetcode Solution169
629House Robber169
630Printing brackets in Matrix Chain Multiplication Problem169
631Minimum Depth of Binary Tree Leetcode Solution169
632Isomorphic Strings169
633Find Sum of all unique sub-array sum for a given array168
634Longest Substring with At Most K Distinct Characters LeetCode Solution168
635Longest Increasing Subsequence168
636Segregate 0s and 1s in an Array168
637Minimum Cost to Hire K Workers168
638Find the Duplicate Number LeetCode Solution168
639Wiggle Sort168
640License Key Formatting Leetcode Solution168
641Count Good Nodes in Binary Tree Leetcode Solution167
642Find Maximum Level sum in Binary Tree167
643Maximum difference between first and last indexes of an element in array167
644Optimal Account Balancing LeetCode Solution167
645Binary Tree Zigzag Level Order Traversal LeetCode Solution167
646Iterative Method to find Height of Binary Tree167
647Coin Change Problem167
648Moving Average from Data Stream Leetcode Solution167
649Sum of All Odd Length Subarrays Leetcode Solution167
650How to Create Mergable Stack?167
651Valid Palindrome II Leetcode Solution167
652Maximum Number of Occurrences of a Substring Leetcode Solution166
653Check If It Is a Straight Line Leetcode Solution166
654Kth Missing Positive Number Leetcode Solution166
655GCD Of Two Numbers166
656Employee Free Time LeetCode Solution166
657Minimum Number of Steps to Make Two Strings Anagram Leetcode Solutions166
658Best Time to Buy and Sell Stock with Cooldown Leetcode Solution166
659Queries for counts of array elements with values in given range166
660Merge Two Balanced Binary Search Trees166
661Strobogrammatic Number LeetCode Solution166
662Convert an array to reduced form165
663Reorganize String165
664Find Largest d in Array such that a + b + c = d165
665Longest Substring with At Least K Repeating Characters LeetCode Solution165
666Flipping an Image LeetCode Solution165
667Find the Distance Value Between Two Arrays Leetcode Solution165
668Number of Provinces Leetcode Solution165
669Letter Combinations of a Phone Number165
670Path With Maximum Minimum Value LeetCode Solution165
671Valid Palindrome165
672Delete consecutive same words in a sequence164
673Maximum Number of Coins You Can Get Leetcode Solution164
674Partition Labels LeetCode Solution164
675Find pairs with given sum such that elements of pair are in different rows164
676Number of Dice Rolls With Target Sum LeetCode Solution163
677Recover Binary Search Tree163
678Edit Distance LeetCode Solution163
679Power of Four Leetcode Solution163
680Factorial Trailing Zeroes Leetcode Solution163
681Valid Perfect Square Leetcode Solution163
682Populating Next Right Pointers in Each Node163
683Longest Increasing Path in a Matrix LeetCode Solution163
684Rearrange an array in order – smallest, largest, 2nd smallest, 2nd largest163
685K Empty Slots163
686Partition Array Into Three Parts With Equal Sum Leetcode Solution163
687Permutation Sequence LeetCode Solution163
688Print the Fibonacci numbers in reverse order163
689Check If Two String Arrays are Equivalent Leetcode Solution163
690Inorder Successor of a node in Binary Tree163
691Reducing Dishes LeetCode Solution163
692Lucky Numbers in a Matrix Leetcode Solution162
693Increasing Decreasing String Leetcode Solution162
694Sort Array by Increasing Frequency Leetcode Solution162
695Merge Two Binary Trees LeetCode Solution162
696Check if a queue can be sorted into another queue using a stack162
697Remove Invalid Parentheses Leetcode Solution162
698BFS vs DFS for Binary Tree162
699String to Integer (atoi) LeetCode Solution162
700Maximum Product of Two Elements in an Array Leetcode Solution162
701Form minimum number from given sequence162
702Construct BST from given Preorder Traversal162
703Dynamic Programming Basics162
704To Lower Case Leetcode Solution162
705Reversing a Queue using Recursion161
706Unique Paths II Leetcode Solution161
707Binary Tree zigzag level order Traversal161
708Convert a Number to Hexadecimal Leetcode Solution161
709Subset Sum Leetcode161
710Find the Smallest Divisor given a Threshold Leetcode Solution161
711Ugly Number Leetcode Solution161
712Find whether an array is subset of another array161
713Robot Room Cleaner Leetcode Solution161
714Reservoir Sampling161
715Reverse Only Letters LeetCode Solution161
716Majority Element II Leetcode Solution160
717Find Leaves of Binary Tree LeetCode Solution160
718Restore IP Addresses Leetcode Solution160
719Keyboard Row Leetcode Solution160
720Binomial Coefficient160
721Delete Nth node from the end of the given linked list160
722Find the largest multiple of 3159
723Find the node with minimum value in a Binary Search Tree159
724Numbers with prime frequencies greater than or equal to k159
725Perform String Shifts Leetcode159
726Add and Search Word – Data structure design LeetCode159
727Bulb Switcher LeetCode Solution159
728Decompress Run-Length Encoded List Leetcode Solution159
729Check if Two Expressions With Brackets are Same159
730Hamming Distance Leetcode Solution158
731Morris Traversal158
732Number of Islands II LeetCode Solution158
733Maximum Product of Three Numbers LeetCode Solution158
734Sum of f(a[i], a[j]) over all pairs in an array of n integers158
735Maximum 69 Number Leetcode Solution158
736Finding K closest element158
737Race Car LeetCode Solution158
738Find Pair with Greatest Product in Array158
739Minimum Cost For Tickets Leetcode Solution158
740Generate all possible sorted arrays from alternate elements of two given sorted arrays158
741Tiling Problem157
742Diagonal Traversal of Binary Tree157
743Minimum Distance Between BST Nodes Leetcode Solution157
744First Unique Character in a String LeetCode Solution157
745Merge K Sorted Linked Lists157
746Invert Binary Tree LeetCode Solution157
747Maximum Depth of N-ary Tree Leetcode Solution157
748Sorted Linked List to Balanced BST157
749Find Maximum Depth of Nested Parenthesis in a String157
750Rank Transform of an Array Leetcode Solution157
751Student Attendance Record I Leetcode Solution157
752String Compression LeetCode Solution157
753Word Pattern LeetCode Solution157
754Special Array With X Elements Greater Than or Equal X Leetcode Solution156
755Kth ancestor of a node in binary tree156
756Symmetric Tree Leetcode Solution156
757Best Meeting Point LeetCode Solution156
758Check If Array Pairs Are Divisible by k LeetCode Solution156
759Binary Tree Maximum Path Sum LeetCode Solution156
760Find unique character in a string156
761Longest Span with same Sum in two Binary arrays156
762Find if Path Exists in Graph Leetcode Solution156
763Non-decreasing Array LeetCode Solution156
764Minimum time required to rot all oranges156
765Minimum Height Trees156
766Remove brackets from an algebraic string containing + and – operators156
767Largest subarray with equal number of 0s and 1s156
768Remove Nth Node From End of List Leetcode Solution156
769Snakes and Ladders LeetCode Solution156
770Find All Duplicates in an Array LeetCode Solution156
771Queue based approach for first non-repeating character in a stream156
772Minimize Maximum Pair Sum in Array LeetCode Solution155
773Largest rectangular sub-matrix whose sum is 0155
774Evaluate Reverse Polish Notation LeetCode Solution155
775Maximum Length of a Concatenated String with Unique Characters Leetcode Solution155
776Partition to K Equal Sum Subsets Leetcode Solution155
777Find Median from Data Stream LeetCode Solution155
778Final Prices With a Special Discount in a Shop Leetcode Solution155
779Largest Rectangle in Histogram LeetCode Solution155
780Search a 2D Matrix II Leetcode Solution155
781Elements to be added so that all elements of a range are present in array155
782Stack Permutations (Check if an array is stack permutation of other)155
783Jump Game155
784Total Numbers With no Repeated Digits in a Range154
785Valid Number154
786Split a String in Balanced Strings Leetcode Solution154
787Program for Bridge and Torch problem154
788k-th missing element in increasing sequence which is not present in a given sequence154
789Transpose Graph154
790Linked List Cycle154
791Count items common to both the lists but with different prices154
792Maximum Difference Between Increasing Elements LeetCode Solution154
793Minimum Jumps to Reach Home LeetCode Solution153
794Last Stone Weight II LeetCode Solution153
795Interval Tree153
796Search in a Binary Search Tree Leetcode Solution153
797Count quadruples from four sorted arrays whose sum is equal to a given value x153
798Growable array based stack153
799Nearest Exit from Entrance in Maze LeetCode Solution153
800Deletion in a Binary Tree153
801Get Maximum in Generated Array Leetcode Solution153
802Sort an array according to the order defined by another array153
803N-Queens LeetCode Solution153
804Base 7 Leetcode Solution153
805One Edit Distance LeetCode Solution153
806Print a Binary Tree in Vertical Order153
807Number of NGEs to the Right153
808Minimum swaps to make sequences increasing152
809Iterative Preorder Traversal152
810Check for Palindrome after every character replacement Query152
811Circular Queue152
812Remove Duplicates from Sorted List II152
813String comparison containing wildcards152
814Course Schedule II – LeetCode152
815Merge Sorted Array LeetCode Solution152
816Remove Duplicates from Sorted List LeetCode Solution152
817Crawler Log Folder Leetcode Solution152
818Maximum Profit in Job Scheduling Leetcode Solution152
819Minimum number of jumps to reach end152
820Subarray Product Less Than K LeetCode Solution152
821A Space Optimized DP solution for 0-1 Knapsack Problem152
822Minimum Time Visiting All Points Leetcode Solution152
823Number Complement Leetcode Solution152
824Priority Queue using doubly linked list152
825Nested List Weight Sum II LeetCode Solution152
826Reorder Data in Log Files LeetCode Solution152
827Relative Ranks Leetcode Solution152
828Longest Subarray Having Count of 1s One More than Count of 0s151
829Form Minimum Number From Given Sequence151
830Maximum size subarray sum equals k151
831Sort Array By Parity II Leetcode Solution151
832Find all triplets with zero sum151
833Spiral Matrix II Leetcode Solution151
834Brick Wall LeetCode Solution150
835Given an Array of Pairs Find all Symmetric Pairs in it150
836Path with maximum average value150
837Make Two Arrays Equal by Reversing Sub-arrays Leetcode Solution150
838Insert into a Binary Search Tree Leetcode Solution150
839Convert BST to Min Heap150
840Find the subarray with least average150
841Valid Parentheses Leetcode Solution150
842Regular Expression Matching150
843Maximum Nesting Depth of the Parentheses Leetcode Solution150
844Alien Dictionary LeetCode Solution150
845Can Place Flowers LeetCode Solution150
846Minimum Number of Taps to Open to Water a Garden LeetCode Solution150
847Sum of nearest smaller and greater number150
848Top K Frequent Words LeetCode Solution149
849Clone Graph LeetCode Solution149
850Level order Traversal in Spiral Form149
851Partition List Leetcode Solution149
852Count Negative Numbers in a Sorted Matrix LeetCode Solution149
853Count Distinct Elements in Every Window of Size K149
854Friends Pairing Problem149
855Subsequence of Size K With the Largest Even Sum LeetCode Solution149
856Find All Possible Recipes from Given Supplies LeetCode Solution149
857Binary Search Tree Search and Insertion149
858Sort Colors149
859Check whether a given Binary Tree is Complete or not149
860Check if a given array can represent Preorder Traversal of Binary Search Tree149
861Subset with sum divisible by m149
862Permutation Coefficient149
863Find the Only Repetitive Element Between 1 to N-1148
864Check if stack elements are pairwise consecutive148
865Brightest Position on Street LeetCode Solution148
866An Interesting Method to generate Binary Numbers from 1 to n148
867Design a Stack With Increment Operation Leetcode Solution148
868Guess Number Higher or Lower LeetCode Solution148
869Tree Traversal (Preorder, Inorder & Postorder)148
870Range LCM Queries148
871Missing Element in Sorted Array LeetCode Solution148
872Find Maximum Sum Possible Equal Sum of Three Stacks148
873Matrix Chain Multiplication148
874Minimum Sum Path in a Triangle148
875Sequences of given length where every element is more than or equal to twice of previous148
876LCS (Longest Common Subsequence) of three strings148
877Balanced Expression with Replacement147
878Identify and Mark Unmatched Parenthesis in an Expression147
879K’th Largest Element in BST when modification to BST is not allowed147
880Best Time to Buy and Sell Stock with Transaction Fee Leetcode Solution147
881Diagonal Traversal LeetCode Solution147
882Design Browser History LeetCode Solution147
883Water Bottles Leetcode Solution147
884Sorted Array to Balanced BST147
885Number of Days Between Two Dates LeetCode Solution147
886Distinct adjacent elements in an array147
887Repeated Substring Pattern LeetCode Solution147
888Diagonal Traverse LeetCode Solution147
889Convert Sorted List to Binary Search Tree147
890Daily Temperatures Leetcode Solution146
891Shortest Word Distance Leetcode Solution146
892Time Based Key-Value Store LeetCode Solution146
893Check if an Array is Stack Sortable146
894Destination City Leetcode Solution146
895Union and Intersection of two Linked Lists146
896Maximum Score After Splitting a String Leetcode Solution146
897Rearrange an Array Such that arr[i] is equal to i146
898Minimum sum of multiplications of n numbers146
899GCDs of given index ranges in an array146
900Insert Delete GetRandom146
901BFS for Disconnected Graph146
902Special Positions in a Binary Matrix Leetcode Solution146
903Guess Number Higher or Lower II146
904Three way partitioning of an array around a given range146
905Robot Bounded In Circle LeetCode Solution145
906Rearrange Array such that arr[i] >= arr[j] if i is even and arr[i] <= arr[j] if i is odd and j < i145
907Range sum queries without updates145
908Find Common Characters Leetcode Solution145
909Minimum Swaps to Make Strings Equal Leetcode Solution145
910Least Number of Unique Integers after K Removals Leetcode Solution145
911Delete And Earn145
912Queue using Stacks145
913Count ways to reach the nth stair using step 1, 2 or 3145
914Spiral Matrix III LeetCode Solution145
915Check if the given array can represent Level Order Traversal of Binary Search Tree145
916Lemonade Change Leetcode Solution145
917Find distance between two nodes of a Binary Tree145
918Construct BST from its given Level Order Traversal144
919Construct Complete Binary Tree from its Linked List Representation144
9204Sum144
921Rearrange Spaces Between Words Leetcode Solution144
922Palindrome Partitioning Leetcode Solution144
923Print Fibonacci sequence using 2 variables144
924Vertical sum in a given binary tree144
925Number of Distinct Islands Leetcode Solution144
926Merge Two Sorted Lists Leetcode144
927Check if any two intervals overlap among a given set of intervals143
928Difference Array | Range update query in O(1)143
929Maximum Frequency Stack Leetcode Solution143
930Set Matrix Zeroes Leetcode Solution143
931Minimum Height Trees LeetCode Solution143
932A program to check if a binary tree is BST or not143
933Maximum Subarray Sum Excluding Certain Elements143
934Construct the Rectangle Leetcode Solution143
935Split Array Into Consecutive Subsequences143
936Stone Game II Leetcode143
937Alien Dictionary143
938Averages of Levels in Binary Tree143
9393 Sum143
940Binary Tree Longest Consecutive Sequence LeetCode Solution142
941Queries for GCD of all numbers of an array except elements in a given range142
942Count Subarrays with Same Even and Odd Elements142
943Analyze User Website Visit Pattern LeetCode Solution142
944Remove Duplicates from Sorted List II LeetCode Solution142
945Trim a Binary Search Tree142
946Iterative Postorder Traversal Using Two Stacks142
947Create Maximum Number142
948Strongly Connected Component142
949Longest Palindromic Subsequence142
950Largest area rectangular sub-matrix with equal number of 1’s and 0’s142
951Lexicographical Numbers Leetcode Solution142
952Infix to Postfix142
953Shuffle 2n integers as a1-b1-a2-b2-a3-b3-..bn without using extra space141
954Unique Paths II141
955Count Submatrices With All Ones LeetCode Solution141
956Number of Equivalent Domino Pairs Leetcode Solution141
957All Unique Triplets that Sum up to a Given Value141
958Collect maximum points in a grid using two traversals141
959Find all permuted rows of a given row in a matrix141
960Sliding Window Maximum141
961Binary array after M range toggle operations141
962Count subarrays where second highest lie before highest140
963Dividing Array into Pairs With Sum Divisible by K140
964Reverse Nodes in K-Group140
965Minesweeper LeetCode Solution140
966Height of a generic tree from parent array140
967Find postorder traversal of BST from preorder traversal140
968Pattern Occurrences using Stack140
969Sign of the Product of an Array LeetCode Solution140
970Can Make Arithmetic Progression From Sequence Leetcode Solution140
971Maximum Product Subarray140
972Word Break140
973Intersection of Two Linked Lists LeetCode Solution140
974Three Consecutive Odds Leetcode Solution140
975Merging Intervals140
976Count pair with Given Sum139
977Median of Two Sorted Arrays139
978Find the Difference Leetcode Solution139
979Symmetric Tree139
980Binary Search Tree Delete Operation139
981The Painter’s Partition Problem139
982Product of Array Except Self LeetCode Solution139
983Longest Nice Substring LeetCode Solution139
984Length of Longest Fibonacci Subsequence139
985Count Primes in Ranges139
986Kth Smallest Element in a BST Leetcode Solution139
987Newman-Conway Sequence139
988Palindrome Partitioning139
989Level Order Traversal of Binary Tree139
990Find Maximum of Minimum for Every Window Size in a Given Array138
991Climbing stairs138
992Segment Tree138
993K Closest Points to Origin Leetcode Solution138
994Asteroid Collision LeetCode Solution138
995My Calendar I LeetCode Solution138
996Check If a Word Occurs As a Prefix of Any Word in a Sentence Leetcode Solution138
997Maximize Sum of Array after K Negations Leetcode Solution138
998Find the First Circular Tour that visits all the Petrol Pumps137
999Depth First Search (DFS) for a Graph137
1000Boundary Traversal of binary tree137
1001Breadth First Search (BFS) for a Graph137
1002Construction of Longest Increasing Subsequence (N log N)137
1003The Maze III LeetCode Solution137
1004Find number of pairs in an array such that their XOR is 0137
1005Largest Number Leetcode Solution137
1006Merge Sort137
1007Largest divisible pairs subset137
1008Compute nCr % p137
1009Maximum Length of Repeated Subarray137
1010Find Duplicate Subtrees137
1011Number of palindromic paths in a matrix137
1012String Matching in an Array Leetcode Solution137
1013Friends Of Appropriate Ages LeetCode Solution137
1014Valid Boomerang Leetcode Solution137
1015Double the first element and move zero to end137
1016Maximum subsequence sum such that no three are consecutive137
1017Shortest Completing Word Leetcode Solution137
1018Maximum Product of Indexes of Next Greater on Left and Right137
1019Number Of Longest Increasing Subsequence137
1020Insertion in a Binary Tree136
1021Scramble String LeetCode Solution136
1022Serialize and Deserialize Binary Tree136
1023Partition Equal Subset Sum136
1024First missing positive136
1025Minimum Index Sum of Two Lists136
1026Level order traversal using two Queues136
1027Binary Search Tree136
1028Make The String Great Leetcode Solution136
1029Kill Process LeetCode Solution136
1030Maximum Number of Ways to Partition an Array LeetCode Solution136
1031Morris Inorder Traversal136
1032Next Greater Element III LeetCode Solution136
1033Boolean Parenthesization Problem136
1034Largest Substring Between Two Equal Characters Leetcode Solution136
1035Graph Valid Tree LeetCode Solution136
1036Construct Binary Tree from given Parent Array representation136
1037Rearrange an array such that ‘arr[j]’ becomes ‘i’ if ‘arr[i]’ is ‘j’136
1038Maximum weight transformation of a given string136
1039Invalid Transactions LeetCode Solution135
1040Count minimum steps to get the given desired array135
1041Decrypt String from Alphabet to Integer Mapping Leetcode Solution135
1042Advantages of BST over Hash Table135
1043Build an Array With Stack Operations Leetcode Solution135
1044Design Hit Counter LeetCode Solution135
1045K maximum sums of overlapping contiguous sub-arrays135
1046Longest subsequence such that difference between adjacents is one135
1047Custom Sort String Leetcode Solution134
1048Available Captures for Rook Leetcode Solution134
1049Ugly Numbers134
1050Validate Binary Search Tree134
1051Rearrange array such that even positioned are greater than odd134
1052Path Sum II LeetCode Solution134
1053Maximum Sum of 3 Non-Overlapping Subarrays134
1054Balanced Binary Tree134
1055Super Ugly Number133
1056Bitwise AND of Numbers Range LeetCode Solution133
1057Defanging an IP Address LeetCode Solution133
1058Maximum difference between frequency of two elements such that element having greater frequency is also greater133
1059Iterative Depth First Traversal of Graph133
1060Implement Trie (Prefix Tree) Leetcode Solution133
1061Employee Importance LeetCode Solution133
1062Count pairs from two sorted arrays whose sum is equal to a given value x133
1063Kth Smallest Element in a Sorted Matrix LeetCode Solution133
1064Ugly Number II LeetCode Solution133
1065Maximum length subsequence with difference between adjacent elements as either 0 or 1133
1066Add two numbers133
1067Populating Next Right Pointers in Each Node Leetcode Solution132
1068Remove Duplicates from Sorted Array II Leetcode Solution132
1069Generate Parentheses Leetcode Solution132
1070Search in Sorted Rotated Array132
1071Find Peak Element132
1072Lowest Common Ancestor132
1073Regular Expression Matching Regular Expression Matching LeetCode Solution132
1074Move all negative elements to end in order with extra space allowed132
1075Recover Binary Search Tree Leetcode Solution132
1076Largest BST Subtree LeetCode Solution131
1077Find a Peak Element II LeetCode Solution131
1078Subarrays with K Different Integers Leetcode Solution131
1079Minimum Size Subarray Sum131
1080Determine Whether Matrix Can Be Obtained By Rotation LeetCode Solution131
1081Root to Leaf path with target sum Leetcode Solutions131
1082Binary Tree Right Side View LeetCode Solution131
1083Number of Students Doing Homework at a Given Time Leetcode Solution131
1084Longest Bitonic Subsequence131
1085Combination Sum IV LeetCode Solution130
1086Rearrange array such that even index elements are smaller and odd index elements are greater130
1087Find whether a subarray is in form of a mountain or not130
1088Clone a Binary Tree with Random Pointers130
1089Number of Closed Islands Leetcode Solution130
1090Smallest Common Region Leetcode Solution130
1091Day of the Year Leetcode Solution130
1092Number of siblings of a given Node in n-ary Tree130
1093Kth Smallest Product of Two Sorted Arrays LeetCode Solution130
1094Maximize Distance to Closest Person LeetCode Solution130
1095Consecutive Characters LeetCode Solution129
1096Find Smallest Range Containing Elements from k Lists129
1097Convert BST into a Min-Heap without using array129
1098Find maximum difference between nearest left and right smaller elements129
1099Find the minimum distance between two numbers129
1100Increasing Triplet Subsequence LeetCode Solution129
1101Count Largest Group Leetcode Solution129
1102Serialize and Deserialize Binary Tree LeetCode Solution129
1103Next Permutation Leetcode Solution129
1104Level of Each node in a Tree from source node129
1105Remove Palindromic Subsequences Leetcode Solution129
1106Distinct Subsequences129
1107Minimum Absolute Difference in BST Leetcode Solution129
1108Binary Tree Data Structure129
1109Types of Binary Tree129
1110Third Maximum Number Leetcode Solution128
1111Divisible Pairs Counting128
1112Constant time range add operation on an array128
1113Path Sum128
1114Palindrome Permutation LeetCode Solution128
1115Cutting a Rod128
1116Remove duplicates from sorted array128
1117Construct Binary Tree from Preorder and Postorder Traversal LeetCode Solution128
1118Print all triplets in sorted array that form AP128
1119Valid Tic-Tac-Toe State LeetCode Solution128
1120Find Three Element From Different Three Arrays Such That a + b + c = sum128
1121Iterative method to find ancestors of a given binary tree128
1122Prime Palindrome LeetCode Solution127
1123Print Next Greater Number of Q queries127
1124Reformat The String Leetcode Solution127
1125Products of ranges in an array127
1126Maximum Product Subarray127
1127Sum of Even Numbers After Queries127
1128Longest Subarray of 1’s After Deleting One Element LeetCode Solution127
1129Search Insert Position126
1130Delete Nodes and Return Forest Leetcode Solution126
1131Mean of Array After Removing Some Elements Leetcode Solution126
1132Thousand Separator Leetcode Solution126
1133Longest Increasing Consecutive Subsequence126
1134Write Code to Determine if Two Trees are Identical126
1135Minimum Score Triangulation of Polygon Leetcode Solution126
1136Print Right View of a Binary Tree126
1137Bottom View of a Binary Tree126
1138Cells with Odd Values in a Matrix LeetCode Solution126
1139Minimum sum of squares of character counts in a given string after removing k characters125
1140Palindromic Substrings Leetcode Solution125
1141Construct K Palindrome Strings LeetCode Solution125
1142Search an Element in Sorted Rotated Array125
1143Merge two BSTs with limited extra space125
1144Moser-de Bruijn Sequence125
1145Topological Sorting125
1146Find maximum length Snake sequence124
1147Swap Nodes In Pairs124
1148Red-Black Tree Introduction124
1149Maximum Product of Splitted Binary Tree LeetCode Solution124
1150Find Two Non-overlapping Sub-arrays Each With Target Sum LeetCode Solution124
1151Maximum Binary Tree124
1152Closest Binary Search Tree Value Leetcode Solution124
1153Subset Sum Problem in O(sum) space124
1154Priority Queue124
1155Bus Routes Leetcode Solution123
1156Check Array Formation Through Concatenation Leetcode Solution123
1157Print modified array after executing the commands of addition and subtraction123
1158Diameter of N-Ary Tree LeetCode Solution123
1159Golomb sequence123
1160Possible Bipartition LeetCode Solution123
1161Web Crawler LeetCode Solution122
1162Find a sorted subsequence of size 3 in linear time122
1163Binary Tree to Binary Search Tree Conversion122
1164Queries for Number of Distinct Elements in a Subarray122
1165Kth Smallest Number in Multiplication Table Leetcode Solution122
1166Transform a BST to Greater sum Tree122
1167Maximize sum of consecutive differences in a circular array122
1168Find Largest Value in Each Tree Row LeetCode Solution122
1169Search Suggestions System LeetCode Solution122
1170Minimum Sideway Jumps LeetCode Solution122
1171Remove Max Number of Edges to Keep Graph Fully Traversable Leetcode Solution122
1172Rotate Array122
1173Matchsticks to Square Leetcode Solution121
1174Find the smallest binary digit multiple of given number121
1175Longest Repeated Subsequence121
1176Count even length binary sequences with same sum of first and second half bits121
1177Compare Strings by Frequency of the Smallest Character Leetcode Solution121
1178Minimum Cost to Move Chips to The Same Position LeetCode Solution121
1179Decision Tree121
1180Graph and its representation121
1181Convert Sorted Array to Binary Search Tree LeetCode Solutions120
1182Factorial Trailing Zeroes LeetCode Solution120
1183First Bad Version120
1184Lowest Common Ancestor in Binary Search Tree120
1185Contiguous Array LeetCode Solution120
1186Swapping Nodes in a Linked List Leetcode Solution120
1187Sum of Left Leaves LeetCode Solution119
1188Decrease Elements To Make Array Zigzag LeetCode Solution119
1189Minimum Moves to Equal Array Elements LeetCode Solution119
1190Maximum sum bitonic subarray119
1191K’th Largest element in BST using constant extra space119
1192Number of Orders in the Backlog Leetcode Solution119
1193Reverse a Path in BST using Queue119
1194Valid Triangle Number119
1195Queue Reconstruction by Height119
1196Moving Stones Until Consecutive Leetcode Solution118
1197Closest Leaf in a Binary Tree LeetCode Solution118
1198Reformat Date LeetCode Solution118
1199Maximum number of segments of lengths a, b and c118
1200Lowest Common Ancestor of a Binary Tree Leetcode Solution118
1201Count Pairs Whose Products Exist in Array118
1202Range Queries for Longest Correct Bracket Subsequence118
1203Given a binary tree, how do you remove all the half nodes?118
1204How to print maximum number of A’s using given four keys118
1205Maximum sum of pairs with specific difference118
1206Array Queries for multiply replacements and product117
1207Guess The Word117
1208Kth Smallest Element in a BST117
1209Champagne Tower LeetCode Solution117
1210Filter Restaurants by Vegan-Friendly, Price and Distance Leetcode Solution116
1211Path Crossing Leetcode Solution116
1212Convert Integer to the Sum of Two No-Zero Integers Leetcode Solution116
1213Replace two consecutive equal values with one greater116
1214Concatenation of Array LeetCode Solution116
1215Minimum Swaps To Make Sequences Increasing LeetCode Solution116
1216Valid Perfect Square LeetCode Solution115
1217Integer Break LeetCode Solution115
1218Range Sum Query using Sparse Table115
1219Write a function to get the intersection point of two Linked Lists115
1220Arithmetic Slices II – Subsequence LeetCode Solution115
1221Perfect Squares LeetCode Solution115
1222Flatten 2D Vector LeetCode Solution115
1223Mean of range in array114
1224Power of Two114
1225Maximum sum of a path in a Right Number Triangle114
1226Design Skiplist LeetCode Solution114
1227New 21 Game114
1228Maximum Depth Of Binary Tree114
1229The kth Factor of n Leetcode Solution114
1230Divide Two Integers Leetcode Solution114
1231Sliding Window Median Leetcode Solution114
1232Check if each internal node of a BST has exactly one child114
1233Check Completeness of a Binary Tree LeetCode Solution114
1234LRU Cache Leetcode Solution114
1235BST to a Tree with Sum of all Smaller Keys114
1236Bold Words in String LeetCode Solution113
1237Check for Identical BSTs without building the trees113
1238Maximum Array from Two given Arrays Keeping Order Same113
1239Longest Common Prefix Using Word by Word Matching113
1240Maximize Elements Using Another Array113
1241Maximum Value at a Given Index in a Bounded Array LeetCode Solution113
1242Find Minimum in Rotated Sorted Array II LeetCode Solution113
1243Check if all levels of two Binary Tree are anagrams or not113
1244Contiguous Array113
1245Queries on Probability of Even or Odd Number in given Ranges113
1246Largest Plus Sign Leetcode Solution113
1247Print modified array after multiple array range increment operations113
1248Print Ancestors of a Given Binary Tree Node Without Recursion112
1249Find k-th smallest element in BST (Order Statistics in BST)112
1250Parallel Courses II LeetCode Solution112
1251Print n terms of Newman-Conway Sequence112
1252Count Subsets Having Distinct Even Numbers111
1253Find minimum number of merge operations to make an array palindrome111
1254Symmetric Tree LeetCode Solution Leetcode Solution111
1255Graph Cloning111
1256Maximum Product Subarray111
1257Merge k Sorted Lists Leetcode Solution111
1258Minimum Remove to Make Valid Parentheses LeetCode Solution110
1259Count and Toggle Queries on a Binary Array110
1260Check if two nodes are on the same path in a Tree110
1261Missing Number110
1262Smallest Range II Leetcode Solution110
1263Next greater element109
1264Verify Preorder Serialization of a Binary Tree109
1265Number of elements less than or equal to a given number in a given subarray109
1266Minimum Time to Collect All Apples in a Tree LeetCode Solution108
1267Check If a String Can Break Another String Leetcode Solution108
1268Excel Sheet Column Title LeetCode Solution108
1269Image Overlap LeetCode Solution108
1270Different Ways to Add Parentheses Leetcode Solution107
1271Palindrome Partitioning107
1272Orderly Queue LeetCode Solution107
1273Min Cost Climbing Stairs LeetCode Solution107
1274Koko Eating Bananas LeetCode Solution107
1275Longest Substring Without Repeating Characters Leetcode Solution105
1276Peeking Iterator LeetCode Solution105
1277Newman–Shanks–Williams prime105
1278Largest Submatrix With Rearrangements LeetCode Solution105
1279Check if X can give change to every person in the Queue105
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
1284Maximum Sum Increasing Subsequence101
1285Arranging Coins Leetcode Solution101
1286Find maximum average subarray of k length100
1287Maximum product of an increasing subsequence100
1288Encoded String With Shortest Length LeetCode Solution100
1289Queries for Decimal Values of Subarrays of a Binary Array99
1290Number of indexes with equal elements in given range99
1291Minimum Total Space Wasted With K Resizing Operations LeetCode Solution99
1292Minimum Number of People to Teach LeetCode Solution98
1293Convert to Base -2 LeetCode Solution98
1294Random Pick Index LeetCode Solution97
1295Reach a Number LeetCode Solution97
1296Convert a BST to a Binary Tree such that sum of all greater keys is added to every key97
1297Check given array of size n can represent BST of n levels or not96
1298Continuous Subarray Sum LeetCode Solution96
1299Find the Winner of the Circular Game LeetCode Solution96
1300Binary Tree to Binary Search Tree Conversion using STL set96
1301Vertical Order Traversal of Binary Tree LeetCode Solution96
1302Add Two Numbers II Leetcode Solution96
1303Jump Game IV LeetCode Solution95
1304Palindrome Number LeetCode Solution95
1305Number of Subsequences That Satisfy the Given Sum Condition LeetCode solution95
1306Queries on XOR of greatest odd divisor of the range95
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
1313Minimum Swaps to Group All 1’s Together Leetcode Solution83
1314Top K Frequent Elements LeetCode Solution83
1315Substring with Concatenation of All Words Leetcode Solution83
1316Binary Tree Inorder Traversal LeetCode Solution81
1317Count Sub Islands LeetCode Solution80
1318Minimum Path Sum 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
1332Stone Game IV LeetCode Solution67
1333Flatten Binary Tree to Linked List LeetCode Solution67
1334Score of Parenthesis 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
1338Is Graph Bipartite? LeetCode Solution62
1339Valid Triangle Number 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
1347Rotate String LeetCode Solution37
1348Excel Sheet Column Number LeetCode Solution37
1349H-Index Leetcode Solution20
1350Maximum Size Subarray Sum Equals k Leetcode Solution20
1351High Five LeetCode Solution19
1352Monotonic Array Leetcode Solution12
1353Insert Delete GetRandom O(1) – Duplicates allowed LeetCode Solution10
1354Unique Binary Search Trees LeetCode Solution10
1355Valid Triangle Number LeetCode Solution8
1356Peak Index in a Mountain Array LeetCode Solution7
1357Swim in Rising Water LeetCode Solution6
1358Isomorphic Strings LeetCode Solution
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