Arrays And String

Question Description Level
1 Plus One Adding one to number represented as array of digits Easy
2 3 Sum Find all triplets with sum Zero Easy
3 Rotate Image Rotate a (N x N) 2D matrix by 90 degree Easy
4 Group Anagrams Groups all the anagrams together Easy
5 Strobogrammatic Number Check if a number is a Strobogrammatic number Easy
6 Substring Without Repeat Longest Substring Without Repeating Characters Medium
7 Mountain Array I Find the peak Index in a Mountain Array Easy
8 Mountain Array II Check for Valid Mountain Array Easy
9 Merge Intervals Merge Overlapping Intervals Medium
10 Meeting Rooms Minimum number of Meeting Rooms required to Accommodate all Meetings Medium
11 String Compare String Compare with Backspace operation Easy
12 Next Closest Time Form the next closest time by reusing the current digits Medium
13 Reverse Number Reverse a 32-bit signed Integer Easy
14 Find Kth Largest Element Find Kth Largest Element in an Array Easy
15 Rotated Sorted Array I Search in Rotated Sorted Array Medium
16 Rotated Sorted Array II Search in Rotated Sorted Array With Duplicate Medium
17 Min in Rotated Sorted Array Find Minimum in Rotated Sorted Array Medium
18 Number is Palindrome How to Check Whether a Number is Palindrome or Not Easy
19 Find Leaders Get all the leaders from an Integer Array Easy
20 Maximum Subarray Sum Maximum Subarray Sum Easy
21 Container With Most Water Calculate area of container with Most Water Medium
22 Valid Parentheses Determine if the input string has valid parentheses combination Easy
23 K Closest Points to Origin Find K Closest Points to Origin Medium
24 Top K Frequent Elements Given a non-empty array of integers, return the k most frequent elements. Medium
25 Minimum Area Rectangle Find Minimum Area Rectangle Medium
26 Missing Ranges Missing Ranges Easy
27 Longest substring with 2 distinct Characters Find the length of the longest substring with 2 distinct Characters Medium
28 Two Sum Find pair from an array with Target Sum Easy
29 Missing from Duplicate arrays Find missing element from duplicate arrays Easy
30 Minimum Window Substring Minimum Window Substring Hard
31 Queue using Two Stacks How can you implement a Queue using Two Stacks Easy
32 Rotation of Array Rotate the array to the right by k steps Easy
33 Max Points on a Line Find the maximum number of points that lie on the same straight line Hard
34 Isomorphic Strings Isomorphic Strings Medium
35 Next Greater Element Given an array, print the Next Greater Element (NGE) for every element Medium
36 Generate valid Parentheses Generate valid Parentheses combinations Medium
37 First Missing Positive Find the First Missing Positive from an Array Hard
38 Rotate Array Rotate Array Easy
39 Flatten Nested List Iterator Flatten Nested List Iterator Medium
40 Search in a 2D Matrix Search for a target value in a 2D Matrix Medium
41 Decode a String Decode a string recursively encoded as count followed by substring Medium
42 First Unique Character in a String First Unique Character in a String Easy
43 3 Sum Closest 3 Sum Closest Medium
44 Robot Return to Origin Robot Return to Origin Easy
45 Minesweeper Game Minesweeper Game - LeetCode Medium
46 Reverse Words in a String Reverse Words in a String Medium
47 Kth Largest Element in a Stream Kth Largest Element in a Stream Easy
48 Squares of a Sorted Array Squares of a Sorted Array Easy
49 Most Profit in Assigning of Work Most Profit in Assigning of Work Medium

Linked List

Question Description Level
1 Remove Nth Last Node Remove Nth Node From End of a Linked List Medium
2 Merge Linked List Merge two sorted Linked List Medium
3 Add Two Numbers Add two numbers represented by Linked List Medium
4 Linked List Palindrome Check if a singly linked list is palindrome or not Medium
5 LinkedList Cycle If there is any Loop in a Singly LinkedList? Medium
6 Find the nth Last Node Find the nth Last node of a Singly LinkedList Medium
7 Intersecting LinkedList Check if 2 LinkedList intersecting each other ? Medium
8 Retain N And Delete M Retain n elements and delete m elements till the end of the List. Medium
9 Reverse a Singly Linked List Reverse a Singly Linked List Medium

Tree And Graph

Question Description Level
1 Binary Tree Maximum Path Sum Find the Binary Tree Maximum Path Sum Hard
2 Serialize and Deserialize Binary Tree Serialize and Deserialize Binary Tree Hard
3 Flip Equivalent Binary Trees Flip Equivalent Binary Trees Medium
4 Count Tree Nodes Counting number of nodes in a Complete Binary Tree Medium
5 Word Search Search a word from a given 2D Board Hard
6 Level Order Traversal Binary Tree Level Order Traversal Medium
7 Level Sum of a Binary Tree Maximum Level Sum of a Binary Tree Medium
8 Zigzag Level Order Traversal Binary Tree Zigzag Level Order Traversal Medium
9 Delete Nodes And Return Forest Delete Nodes And Return Forest from a Binary Tree Medium
10 Find Number of Islands I Find Number of Islands I Medium
11 Longest Increasing Path in a Matrix Longest Increasing Path in a Matrix Hard
12 Lowest Common Ancestor Find the lowest common ancestor of two nodes in a Binary Tree Medium
13 Vertical Order Traversal Vertical Order Traversal of a Binary Tree Medium
14 Sorted array to BST Convert a sorted array to a Binary Search Tree Easy
15 All root-to-leaf paths Given a binary tree, return all root-to-leaf paths Medium
16 Sum Root to Leaf Numbers Sum Root to Leaf Numbers Medium
17 Root to Leaf Paths With Sum Root to Leaf Paths With Sum Medium
18 Kth Smallest Element in a BST Kth Smallest Element in a BST Medium
19 Maximum Depth of Binary Tree Maximum Depth of Binary Tree Easy
20 Subtree of Another Tree Subtree of Another Tree Easy
21 Cousins in Binary Tree Cousins in Binary Tree Easy
22 BST Iterator Binary Search Tree Iterator Medium
23 Boundary Of Binary Tree Boundary Traversal Of Binary Tree Medium
24 Serialize and Deserialize N-ary tree Serialize and Deserialize N-ary tree Hard
25 Most Frequent Subtree Sum Most Frequent Subtree Sum Medium
26 Minimum steps to reach target by a Knight in a Chess Board Minimum steps to reach target by a Knight in a Chess Board Medium
27 Nodes which don’t have Sibling Print all nodes of a Binary Tree that don’t have sibling Medium

Recusrion

Question Description Level
1 Calculate GCD Calculate GCD (Greatest common divisor) of 2 numbers recursively Easy
2 Min Cost to Climbing Stairs Min Cost to Climbing Stairs Easy
3 Letter Combinations of a Phone Number Letter Combinations of a Phone Number Medium

Dynamic Programming

Question Description Level
1 Find Unique Paths I Find Unique Paths in a 2D Grid from Source to Destination Medium
2 Find Unique Paths II Unique Paths in a 2D Grid with Obstacle Medium
3 Unique Paths III Unique Paths III Hard
4 Maximum Product Subarray Find maximum product subarray Easy
5 Interleaving String Interleaving String Hard
6 Climbing Stairs Climbing Stairs Easy
7 Gas Station Gas Station Easy

Designing Problems

Question Description Level
1 Design a Min Stack Design a Stack that supports getMin() in O(1) time | Min Stack Easy
2 LRU Cache Design a LRU Cache Medium

Others

Question Description Level
1 My Calendar I My Calendar I Medium
2 My Calendar II My Calendar II Medium
3 Solving a Maze by Backtracking Solving a Maze by Backtracking Hard
4 Maximum Frequency Stack Maximum Frequency Stack Hard
5 Broken Calculator Broken Calculator Easy