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2026-03-27 Valid Parentheses 2026-03-26 Two Sum 2026-03-25 Binary Tree Level Order Traversal 2026-03-24 Number of Islands

270 problems

✔ Title Topic Difficulty Platform
◯ 3Sum Array Medium LeetCode
◯ 3Sum Closest Array Medium LeetCode
◯ 4Sum Array Medium LeetCode
◯ Add Binary Matrix Easy LeetCode
◯ Add Two Numbers Linked-List Medium LeetCode
◯ Add Two Numbers II Linked-List Medium LeetCode
◯ Alien Dictionary Graph Hard Other
◯ All Nodes Distance K in Binary Tree Tree Medium LeetCode
◯ Allocate Minimum Pages | Practice Sorting&Searching Hard GeeksforGeeks
◯ As Far from Land as Possible Graph Medium LeetCode
◯ Backspace String Compare Stack&Queue Easy LeetCode
◯ Balanced Binary Tree Tree Easy LeetCode
◯ Basic Calculator II String Medium LeetCode
◯ Beautiful Arrangement Backtracking Medium LeetCode
◯ Best Time to Buy and Sell Stock Array Easy LeetCode
◯ Best Time to Buy and Sell Stock II Array Easy LeetCode
◯ Best Time to Buy and Sell Stock IV Dynamic-Programming Hard LeetCode
◯ BFS of graph | Practice Graph Easy GeeksforGeeks
◯ Binary Search Tree Iterator Tree Medium LeetCode
◯ Binary Tree Cameras Tree Hard LeetCode
◯ Binary Tree Level Order Traversal Daily Tree Medium LeetCode
◯ Binary Tree Maximum Path Sum Tree Hard LeetCode
◯ Binary Tree Paths Tree Easy LeetCode
◯ Binary Tree Right Side View Tree Medium LeetCode
◯ Binary Tree Zigzag Level Order Traversal Tree Medium LeetCode
◯ Boyer Moore Algorithm for Pattern Searching String Hard GeeksforGeeks
◯ BST with Dead End | Practice Tree Easy GeeksforGeeks
◯ Burst Balloons Dynamic-Programming Hard LeetCode
◯ Ceiling in a sorted array Sorting&Searching Easy GeeksforGeeks
◯ Cheapest Flights Within K Stops Graph Medium LeetCode
◯ Check if it is possible to finish all task from given dependencies (Course Schedule I) Graph Medium GeeksforGeeks
◯ Check if reversing a sub array make the array sorted Sorting&Searching Medium GeeksforGeeks
◯ Check whether a given graph is Bipartite or not Graph Medium GeeksforGeeks
◯ Chocolate Distribution Problem Array Easy GeeksforGeeks
◯ Climbing Stairs Dynamic-Programming Easy LeetCode
◯ Coin Change Dynamic-Programming Medium LeetCode
◯ Combinations Backtracking Medium LeetCode
◯ Construct Binary Tree from Preorder and Postorder Traversal Tree Medium LeetCode
◯ Construct BST from Preorder Traversal Tree Hard GeeksforGeeks
◯ Container With Most Water Array Medium LeetCode
◯ Convert Binary Number in a Linked List to Integer Linked-List Easy LeetCode
◯ Convert Sorted Array to Binary Search Tree Tree Easy LeetCode
◯ Copy List with Random Pointer Linked-List Medium LeetCode
◯ Count BST nodes that lie in a given range | Practice Tree Medium GeeksforGeeks
◯ Count Different Palindromic Subsequences Dynamic-Programming Hard LeetCode
◯ Count of Smaller Numbers After Self Sorting&Searching Hard LeetCode
◯ Count Square Submatrices with All Ones Dynamic-Programming Medium LeetCode
◯ Counting Bits Dynamic-Programming Easy LeetCode
◯ Critical Connections in a Network Graph Hard LeetCode
◯ Daily Temperatures Stack&Queue Medium LeetCode
◯ Decode String Graph Medium LeetCode
◯ Decode Ways Dynamic-Programming Medium LeetCode
◯ Delete and Earn Dynamic-Programming Medium LeetCode
◯ Depth First Search or DFS for a Graph Graph Easy GeeksforGeeks
◯ Design Add and Search Words Data Structure Tries Medium LeetCode
◯ Detect a negative cycle in a Graph | (Bellman Ford) Graph Medium GeeksforGeeks
◯ Detect Cycle in a Directed Graph Graph Easy GeeksforGeeks
◯ Diameter of Binary Tree Tree Easy LeetCode
◯ Distance of nearest cell having 1 | Practice Stack&Queue Medium GeeksforGeeks
◯ Distinct Subsequences String Hard LeetCode
◯ Evaluate Division Graph Medium LeetCode
◯ Evaluate Reverse Polish Notation Stack&Queue Medium LeetCode
◯ Evaluation of Postfix Expression Stack&Queue Easy GeeksforGeeks
◯ Excel Sheet Column Title Matrix Easy LeetCode
◯ Find All Duplicates in an Array Array Medium LeetCode
◯ Find Eventual Safe States Graph Medium LeetCode
◯ Find Maximum number possible by doing at-most K swaps Backtracking Hard GeeksforGeeks
◯ Find median of BST Tree Hard GeeksforGeeks
◯ Find paths from corner cell to middle cell in maze Backtracking Hard GeeksforGeeks
◯ Find Peak Element Sorting&Searching Medium LeetCode
◯ Find the City With the Smallest Number of Neighbors at a Threshold Distance Graph Medium LeetCode
◯ Find the Duplicate Number Array Easy LeetCode
◯ Find the Index of the First Occurrence in a String String Easy LeetCode
◯ Flatten a Multilevel Doubly Linked List Linked-List Medium LeetCode
◯ Flatten Binary Tree to Linked List Tree Medium LeetCode
◯ Flatten Nested List Iterator Stack&Queue Medium LeetCode
◯ Flattening a Linked List Linked-List Hard GeeksforGeeks
◯ Flood Fill Graph Easy LeetCode
◯ Floyd Warshall | Practice Graph Medium GeeksforGeeks
◯ Frog Jump Dynamic-Programming Hard LeetCode
◯ Game of Life Array Medium LeetCode
◯ Gas Station | Practice Stack&Queue Medium GeeksforGeeks
◯ Generate Parentheses String Medium LeetCode
◯ Given a matrix of ‘O’ and ‘X’, replace ‘O’ with ‘X’ if surrounded by ‘X’ Matrix Medium GeeksforGeeks
◯ Given only a pointer/reference to a node to be deleted in a singly linked list, how do you delete it? Linked-List Easy GeeksforGeeks
◯ Happy Number Matrix Easy LeetCode
◯ https://leetcode.com/problems/binary-tree-inorder-traversal/ Tree Easy LeetCode
◯ https://practice.geeksforgeeks.org/problems/binary-tree-to-dll/1 Tree Hard GeeksforGeeks
◯ Implement Queue using Stacks Stack&Queue Easy LeetCode
◯ Implement Stack and Queue using Deque Stack&Queue Easy GeeksforGeeks
◯ Implement Stack using Queues Stack&Queue Easy LeetCode
◯ Implement two Stacks in an Array Stack&Queue Easy GeeksforGeeks
◯ Insert Delete GetRandom O(1) - Duplicates allowed Array Hard LeetCode
◯ Integer to English Words String Hard LeetCode
◯ Integer to Roman String Medium LeetCode
◯ Intersection of Two Linked Lists Linked-List Easy LeetCode
◯ Introduction to Graph Coloring Graph Medium GeeksforGeeks
◯ Invert Binary Tree Tree Easy LeetCode
◯ Jump Game Array Medium LeetCode
◯ K-th Symbol in Grammar Backtracking Medium LeetCode
◯ Knight Dialer Dynamic-Programming Medium LeetCode
◯ Kth Smallest Element in a BST Tree Medium LeetCode
◯ Largest area rectangular sub-matrix with equal number of 1’s and 0’s Dynamic-Programming Hard GeeksforGeeks
◯ Largest BST in a Binary Tree Tree Hard GeeksforGeeks
◯ Largest Rectangle in Histogram Array Hard LeetCode
◯ Letter Combinations of a Phone Number Stack&Queue Medium LeetCode
◯ Linked List Cycle Linked-List Easy LeetCode
◯ Longest Common Prefix String Easy LeetCode
◯ Longest Common Substring | Practice Dynamic-Programming Medium GeeksforGeeks
◯ Longest Happy Prefix String Hard LeetCode
◯ Longest Increasing Path in a Matrix Graph Hard LeetCode
◯ Longest Increasing Subsequence Dynamic-Programming Medium LeetCode
◯ Longest Repeating Character Replacement Two-Pointer Medium LeetCode
◯ Lowest Common Ancestor of a Binary Search Tree Tree Easy LeetCode
◯ Lowest Common Ancestor of a Binary Tree Tree Medium LeetCode
◯ LRU Cache – Complete Tutorial Stack&Queue Hard GeeksforGeeks
◯ M-Coloring Problem | Practice Backtracking Medium GeeksforGeeks
◯ Majority Element Array Easy LeetCode
◯ Make all array elements equal with minimum cost Sorting&Searching Medium GeeksforGeeks
◯ Making A Large Island Graph Hard LeetCode
◯ Max Points on a Line Matrix Medium LeetCode
◯ Max Value of Equation Array Hard LeetCode
◯ Maximal Rectangle Dynamic-Programming Hard LeetCode
◯ Maximal Square Dynamic-Programming Medium LeetCode
◯ Maximize The Cut Segments | Practice Dynamic-Programming Medium GeeksforGeeks
◯ Maximum Depth of Binary Tree Tree Easy LeetCode
◯ Maximum Length of Repeated Subarray Dynamic-Programming Medium LeetCode
◯ Maximum Number of Visible Points Two-Pointer Medium LeetCode
◯ Maximum of minimums of every window size in a given array Stack&Queue Hard GeeksforGeeks
◯ Maximum Points You Can Obtain from Cards Array Medium LeetCode
◯ Maximum Product of Three Numbers Matrix Easy LeetCode
◯ Maximum Product Subarray Dynamic-Programming Easy LeetCode
◯ Maximum size rectangle binary sub-matrix with all 1s Matrix Medium GeeksforGeeks
◯ Maximum Width of Binary Tree Tree Medium LeetCode
◯ Merge k Sorted Lists Linked-List Hard LeetCode
◯ Merge Sort for Linked Lists Linked-List Hard GeeksforGeeks
◯ Merge Sorted Array Array Easy LeetCode
◯ Merge Two Binary Trees Tree Easy LeetCode
◯ Merge Two Sorted Lists Linked-List Easy LeetCode
◯ Middle of the Linked List Linked-List Easy LeetCode
◯ Min distance between two given nodes of a Binary Tree | Practice Tree Medium GeeksforGeeks
◯ Minimize Cash Flow among a given set of friends who have borrowed money from each other Graph Hard GeeksforGeeks
◯ Minimum Absolute Difference in BST Tree Easy LeetCode
◯ Minimum Cost to Hire K Workers Heap Hard LeetCode
◯ Minimum Cost to Merge Stones Dynamic-Programming Hard LeetCode
◯ Minimum Cost Tree From Leaf Values Stack&Queue Medium LeetCode
◯ Minimum Insertion Steps to Make a String Palindrome Dynamic-Programming Hard LeetCode
◯ Minimum Moves to Equal Array Elements Matrix Easy LeetCode
◯ Minimum Number of Refueling Stops Heap Hard LeetCode
◯ Minimum Path Sum Dynamic-Programming Medium LeetCode
◯ Minimum swaps to sort an array Sorting&Searching Hard GeeksforGeeks
◯ Minimum Window Substring String Hard LeetCode
◯ Missing Number Matrix Easy LeetCode
◯ Mobile numeric keypad | Practice Dynamic-Programming Medium GeeksforGeeks
◯ Most Stones Removed with Same Row or Column Graph Medium LeetCode
◯ Move Zeroes Array Easy LeetCode
◯ Multiply two numbers represented by Linked Lists Linked-List Easy GeeksforGeeks
◯ N-Queens Backtracking Hard LeetCode
◯ Next Greater Element I Stack&Queue Easy LeetCode
◯ Number of Islands Daily Matrix Medium GeeksforGeeks
◯ Number of Operations to Make Network Connected Graph Medium LeetCode
◯ Ones and Zeroes Dynamic-Programming Easy LeetCode
◯ Online Stock Span Stack&Queue Medium LeetCode
◯ Optimal Binary Search Tree Dynamic-Programming Hard GeeksforGeeks
◯ Pair with the given difference Sorting&Searching Easy GeeksforGeeks
◯ Palindrome Linked List Linked-List Easy LeetCode
◯ Palindrome Number Matrix Easy LeetCode
◯ Palindrome Pairs Tries Hard LeetCode
◯ Palindrome Partitioning Backtracking Medium LeetCode
◯ Partition List Linked-List Medium LeetCode
◯ Partition of a set into K subsets with equal sum Backtracking Hard GeeksforGeeks
◯ Path Sum Tree Easy LeetCode
◯ Path Sum III Tree Medium LeetCode
◯ Permutations II Backtracking Medium LeetCode
◯ Permute two arrays such that sum of every pair is greater or equal to K Sorting&Searching Easy GeeksforGeeks
◯ Phone Directory Tries Hard Other
◯ Populating Next Right Pointers in Each Node Tree Medium LeetCode
◯ Power of Two Matrix Easy LeetCode
◯ Predecessor and Successor | Practice Tree Easy GeeksforGeeks
◯ Preorder to BST | Practice Tree Medium GeeksforGeeks
◯ Prim’s Algorithm for Minimum Spanning Tree (MST) Graph Medium GeeksforGeeks
◯ Print all combinations | Set-2 Array Medium GeeksforGeeks
◯ Print all k-sum paths in a binary tree Tree Hard GeeksforGeeks
◯ Print all Palindromic Partitions of a String using Bit Manipulation Backtracking Hard GeeksforGeeks
◯ Print all the duplicate characters in a string String Easy GeeksforGeeks
◯ Print Anagrams Together | Practice Tries Medium GeeksforGeeks
◯ Product of Array Except Self Sorting&Searching Medium GeeksforGeeks
◯ Radix Sort – Data Structures and Algorithms Tutorials Sorting&Searching Medium GeeksforGeeks
◯ Range Sum of BST Tree Easy LeetCode
◯ Range Sum Query 2D - Immutable Dynamic-Programming Medium LeetCode
◯ Rat in a Maze Problem - I | Practice Graph Easy GeeksforGeeks
◯ Rearrange a given linked list in-place Linked-List Medium GeeksforGeeks
◯ Rearrange a Linked List in Zig-Zag fashion Linked-List Medium GeeksforGeeks
◯ Recover Binary Search Tree Tree Medium LeetCode
◯ Redundant Connection Tree Medium LeetCode
◯ Remove Boxes Graph Hard LeetCode
◯ Remove Duplicates from Sorted Array Array Easy LeetCode
◯ Remove Duplicates from Sorted List Linked-List Easy LeetCode
◯ Remove Duplicates from Sorted List II Linked-List Medium LeetCode
◯ Remove Linked List Elements Linked-List Easy LeetCode
◯ Remove Nth Node From End of List Linked-List Medium LeetCode
◯ Reorder List Linked-List Medium LeetCode
◯ Reverse Integer Matrix Easy LeetCode
◯ Reverse Linked List Linked-List Easy LeetCode
◯ Reverse Linked List II Linked-List Medium LeetCode
◯ Reverse Nodes in k-Group Linked-List Hard LeetCode
◯ Reverse Pairs Array Hard LeetCode
◯ Reverse Words in a String String Medium LeetCode
◯ Rotate Image Matrix Medium LeetCode
◯ Rotten Oranges | Practice Stack&Queue Medium GeeksforGeeks
◯ Same Tree Tree Easy LeetCode
◯ Search in Rotated Sorted Array Sorting&Searching Hard LeetCode
◯ Segregate even and odd nodes in a Linked List Linked-List Medium GeeksforGeeks
◯ Serialize and Deserialize Binary Tree Tree Hard LeetCode
◯ Set Matrix Zeroes Array Easy LeetCode
◯ Shortest Bridge Graph Medium LeetCode
◯ Simplify Path String Medium LeetCode
◯ Sliding Window Maximum Heap Hard LeetCode
◯ Snakes and Ladders Graph Medium LeetCode
◯ Solving Cryptarithmetic Puzzles Backtracking Hard GeeksforGeeks
◯ Sort a linked list of 0s, 1s and 2s Linked-List Easy GeeksforGeeks
◯ Sort Colors Array Medium LeetCode
◯ Sort Colors (One-Pass, Constant Space) Two-Pointer Medium LeetCode
◯ Sort List Linked-List Medium LeetCode
◯ Spiral Matrix Array Medium LeetCode
◯ Split Array Largest Sum Sorting&Searching Hard LeetCode
◯ SPOJ.com - Problem AGGRCOW Sorting&Searching Hard Other
◯ Steps by Knight | Practice Graph Medium GeeksforGeeks
◯ Strongly Connected | Practice Graph Medium GeeksforGeeks
◯ Subarray Sum Equals K Array Medium LeetCode
◯ Subarray Sums Divisible by K Array Medium LeetCode
◯ Subset Sum Problem Backtracking Medium GeeksforGeeks
◯ Subsets II Backtracking Medium LeetCode
◯ Subtract Two Numbers represented as Linked Lists Linked-List Hard GeeksforGeeks
◯ Subtree of Another Tree Tree Easy LeetCode
◯ Sudoku Solver Backtracking Hard LeetCode
◯ Sum of Distances in Tree Tree Hard LeetCode
◯ Sum of Left Leaves Tree Easy LeetCode
◯ Sum of Subarray Minimums Stack&Queue Medium LeetCode
◯ Super Egg Drop Dynamic-Programming Hard LeetCode
◯ Swim in Rising Water Heap Hard LeetCode
◯ Symmetric Tree Tree Easy LeetCode
◯ Text Justification String Hard LeetCode
◯ The Celebrity Problem Stack&Queue Hard GeeksforGeeks
◯ The kth Factor of n Matrix Medium LeetCode
◯ Time Needed to Inform All Employees Graph Medium LeetCode
◯ Topological sort | Practice Graph Medium GeeksforGeeks
◯ Total number of Spanning Trees in a Graph Graph Hard GeeksforGeeks
◯ Trapping Rain Water Dynamic-Programming Hard LeetCode
◯ Travelling Salesman Problem using Dynamic Programming Graph Hard GeeksforGeeks
◯ Trie Data Structure Tries Medium GeeksforGeeks
◯ Tug of War Backtracking Hard GeeksforGeeks
◯ Two Sum Daily Array Easy LeetCode
◯ Undirected Graph Cycle | Practice Graph Easy GeeksforGeeks
◯ Unique Binary Search Trees Tree Medium LeetCode
◯ Unique Binary Search Trees II Tree Medium LeetCode
◯ Unique Paths Dynamic-Programming Medium LeetCode
◯ Unique Paths III Backtracking Hard LeetCode
◯ Valid Number String Hard LeetCode
◯ Valid Palindrome II String Easy LeetCode
◯ Valid Parentheses Daily String Easy LeetCode
◯ Valid Square Matrix Medium LeetCode
◯ Validate Binary Search Tree Tree Medium LeetCode
◯ Vertical Order Traversal of a Binary Tree Tree Hard LeetCode
◯ Water Jug problem using BFS Graph Hard GeeksforGeeks
◯ Weighted Job Scheduling Dynamic-Programming Medium GeeksforGeeks
◯ Word Break Problem | (Trie solution) Tries Medium GeeksforGeeks
◯ Word Ladder Graph Hard LeetCode
◯ Word Search Array Medium LeetCode
◯ Word Search II Backtracking Hard LeetCode