Most Asked Problems in Data Structures and Algorithms

This sheet provides a wide range of questions on data structures and algorithms. It includes dynamic and trending topics that match industry-level requirements. Firstly, you have to learn any programming language like C, C++, Java, etc. and after getting a better understanding of the concepts and language specifics,practice these questions for the mastery of DSA.

Here is a list of topics featuring the most frequently asked problems in Data Structures and Algorithms:

• Array
• String
• Stack
• Queue
• Linked List
• Tree
• Tries
• Dynamic Programming
• Graph
• Matrix
• Backtracking
• Binary Search
• Math & Bit Manipulation
• Heap
• Advanced-Data Structures

Array Problems

An array is a collection of elements present in a contiguous memory location. Its most asked problems are the following:

• Sum of two array elements
• Best Time to Buy and Sell Stock
• Contains Duplicate
• Maximum Subarray
• Merge Intervals
• 3Sum
• Container With Most Water
• Rotate Image
• Merge Sorted Array
• Rotate Array
• Remove Element
• Find Peak Element
• Remove Duplicates from the Sorted Array

String Problems

A string is a series of characters stored in a specific order. Here are the String's most common problems:

• Group Anagrams
• Longest Palindromic Substring
• Longest Substring Without Repeating Characters
• Minimum Window Substring
• Valid Palindrome
• Valid Anagram
• Reverse String
• First Unique Character in String

Stack Problems

Stack follows the principle of last in first out(LIFO). Stack data structure problems are given below:

• Min Stack
• Implement Stack using Queues
• Valid Parentheses
• Longest Valid Parentheses
• Score of Parentheses
• Basic Calculator
• Evaluate Reverse Polish Notation
• Basic Calculator II

Queue Problems

A queue follows the principle of first in first out(FIFO). Queue data structure problems are the following:

• Find Median from Data Stream
• Top K Frequent Elements
• Design Circular Queue
• Moving Average from Data Stream
• Sliding Window Maximum
• Task Scheduler

Linked List Problems

Linked List organizes a sequence of elements in a linear arrangement. The top problems of linked lists are given below:

• Merge Two Sorted Lists
• Linked List Cycle
• Reverse Linked List
• Middle of the Linked List
• Remove Nth Node From End of List
• Add Two Numbers
• Copy List with Random Pointer
• Merge k Sorted Lists
• Reverse Nodes in k-Group
• Sort List

Tree (Binary Tree and BST) Problems

A tree represents a collection of elements in a hierarchical format. The following are the tree's most common problems:

• Invert Binary Tree
• Maximum Depth of Binary Tree
• Diameter of Binary Tree
• Convert Sorted Array to Binary Search Tree
• Symmetric Tree
• Validate Binary Search Tree
• Kth Smallest Element in a BST
• Binary Tree Zigzag Level Order Traversal
• Flatten Binary Tree to Linked List
• Path Sum
• Binary Tree Right Side View
• Binary Tree Level Order Traversal
• Minimum Absolute Difference in BST

Tries Problems

Tries is a data structure that stores strings in a structure like a tree. Its most searched problems are given below:

• Implement Trie (Prefix Tree)
• Word Search II

Dynamic Programming Problems

Dynamic Programming divides the problems into subproblems. The following are the best problems to learn DP:

• Climbing Stairs
• House Robber
• Maximal Square
• Word Break
• Coin Change
• Longest Increasing Subsequence
• Unique Paths

Graph Problems

A graph organizes a collection of elements in a non-linear manner. Graphs best problems are given below:

• Number of Islands
• Course Schedule
• Course Schedule II

Matrix Problems

A matrix is also known as a 2D array. Its logical and hard problems are the following:

• Search a 2D Matrix
• Valid Sudoku
• Find Word
• Rotate Image
• Set Matrix Zeroes
• Spiral Matrix
• Search a 2D Matrix II

Backtracking Problems

The backtracking algorithm constructs the solution by exploring all potential options. The best way to learn this is by solving given problems:

• Permutations
• Subsets
• Combination Sum
• Letter Combinations of a Phone Number
• Generate Parentheses

Binary Search Problems

Binary Search is a method for finding an item in a sorted array by repeatedly halving the search range. The following are the best topics to master in Binary Search:

• Binary Search Implementation
• Search in Rotated Sorted Array
• Find Minimum in Rotated Sorted Array
• Median of Two Sorted Arrays

Math & Bit Manipulation Problems

Bit Manipulation is a strategy employed in numerous problems to derive solutions more efficiently. The following are the good problems to learn Bit manipulation

• Number of 1 Bits
• Pow(x, n)
• Palindrome Number
• Sqrt(x)
• Bitwise AND of Numbers Range

Heap Problems

A heap is a tree-based data structure its top problems are given below:

• Kth Largest Element in an Array
• Find Median from Data Stream
• Top K Frequent Elements

Advanced-Data Structures Problems

Advanced data Structures are the specialized formats of data, here are some good topics:

• Longest Consecutive Sequence
• Jump Game
• Trapping Rain Water