Must Do Coding Questions for Product Based Companies

As the placement season is back, GeeksforGeeks is here to help you crack the interview. We have selected some most commonly asked and MUST DO practice problems to crack Product-based Company Interviews.

You can also take part in our mock placement contests which will help you learn different topics and practice at the same time, simulating the feeling of a real placement test environment.

If you are looking for Old MUST DO list, please refer MUST DO Coding Problems for Companies like Amazon, Microsoft, Adobe, …

In case you are a new user, we strongly recommend you to go through the below Improved list.

Note: Now you can track your progress of these questions Must Do Interview Preparation Course.

Topic:

Math

• Easy
  • Missing Number in Array
  • Trailing Zeros in Factorial
• Medium
  • A Simple Fraction
• Hard
  • Nth Natural Number
  • Smallest Positive Integer that can not be represented as Sum

Arrays

• Easy
  • Rotate Array
  • Majority Element
  • Plus one
  • Array of alternative +ve and -ve no.s
  • Product Array puzzle
  • Frequencies of Limited Range Array Elements
  • Large Factorial
• Medium
  • Jump Game
  • Maximum number of 1’s
  • Stock Buy and Sell
  • Longest Consecutive Subsequence
  • Maximum value of difference of a pair of elements and their Index
  • Maximum index
  • K-th element of two sorted Arrays
  • Trapping Rain Water
  • 3 sum closest
• Hard 
  • Maximum circular Subarray Sum
  • Merge without Extra Space

Searching

• Easy
  • Search insert position of K in a sorted array
  • Collecting Wood
  • Left most and right most index
  • Bitonic Point 
• Medium
  • Search an element in sorted and rotated array
  • Square root of a number
  • Find missing in second array
• Hard
  • Painter’s Partition Problem
  • Median of 2 sorted arrays of Different sizes
  • Allocate minimum number of pages

Sorting

• Easy
  • Wave array
• Medium
  • Count the number of possible triangles
  • Triplets with sum with given range
  • Count Inversions
  • Relative Sorting
  • Minimum Platforms
  • Maximum Index

Matrix

• Easy 
  • Sort  a 2D vector diagonally
• Medium
  • Spiral Matrix
  • Boolean matrix
  • Rotate matrix by 90 degrees
  • Search in a row-column sorted Matrix
  • Row with maximum 1s

String

• Easy 
  • Reverse words in a given string
  • Longest Common Prefix
  • Roman Number to Integer
• Medium
  • Next higher palindrome number using the same set of digits
  • Length of longest prefix suffix
  • Smallest window in string containing all characters
  • Validate an IP address
  • Implement Atoi
  • Look and say Pattern
  • Longest K unique characters substring

Hashing

• Easy 
  • Key Pair
  • Top K Frequent Elements in Array
  • Intersection of two arrays
  • Array Pair Sum Divisibility Problem
• Medium
  • Triplet Sum in Array
  • Length of the longest substring
  • Is Sudoku Valid
  • Print Anagrams Together 
  • Subarrays with sum K
  • Longest subarray with sum divisible by K

Bit Masking

• Easy 
  • Reverse bits
  • Number of set bits
  • Sum of two integers
  • Check whether K-th bit is set or not
  • Longest Consecutive 1’s
• Medium 
  • Find the element that appears once
  • Gray code
  • Maximum AND
• Hard 
  • Maximum subset XOR
  • Bit Difference

Linked List

• Easy
  • Merge Two Sorted Linked Lists
  • Reverse a Linked List
  • Delete a Node without Head Pointer
  • Add two Numbers represented by linked lists
  • Finding middle element in a linked list
  • Check if linked list is palindrome
• Medium
  • Rearrange a linked list
  • Detect and Remove a loop In Linked List
  • Merge Sort for Linked List
  • Intersection of Linked List
  • Rotate Linked List by K places
  • Flattening a Linked List
  • Reverse a linked list in groups of given size
  • Partition a linked list around a given value
• Hard
  • Clone a linked list with next and random pointers

Stack

• Easy
  • Parenthesis Checker
  • Infix to Postfix
  • Restrictive Candy Crush
• Medium
  • Next Larger Element 
  • Stock span problem
  • The Celebrity Problem
  • Maximum Rectangular Area in a Histogram 
• Hard
  • Longest Valid Parentheses
  • Maximum of minimum for every window size
  • Remove K digits
  • 132 Geeky Buildings

Queue

• Medium
  • Maximum of all subarrays of size K
  • Circular tour (Sliding Window)

Heap

• Easy
  • Rearrange Characters
  • Minimum Cost of ropes
• Medium
  • Kth largest element of stream
  • Merge k sorted arrays
• Hard
  • Median of stream

Binary Tree

• Easy
  • Symmetric Tree
  • Zigzag Tree Traversal
  • Checked for Balanced tree
  • Height of Binary Tree
  • Diameter of Binary tree
  • Determine if two trees are identical
  • Minimum depth of binary tree
• Medium
  • Check if subtree
  • Inorder Traversal (iterative)
  • Preorder Traversal (iterative)
  • Postorder Traversal(iterative)
  • Vertical Traversal of a Binary Tree
  • Construct Binary Tree from Preorder and Inorder Traversal
  • Connect nodes at same level
  • Lowest Common Ancestor of a Binary Tree
  • Boundary Traversal
  • Sum tree
• Hard
  • Binary Tree to Doubly Linked List
  • Maximum sum path between two leaf nodes
  • Burning Tree

Binary Search Tree

• Easy
  • Check for BST
  • Array to BST
  • Inorder Successor in BST
  • Kth Largest Element in a BST
• Medium
  • Remove BST keys outside the given range
  • Pair with given target in BST
  • Unique BSTs
  • Preorder Traversal and BST
• Hard
  • Merge two BST’s
  • Fixing two nodes of a BST

Graph

• Medium
  • Number of Islands
  • COVID Spread
  • Prerequisite tasks
  • Strongly Connected Component
  • Minimum swaps to sort
  • Shortest path
  • Circle of Strings
  • Snake and Ladder Problem 
  • Detect cycle in an undirected graph
  • Detect cycle in a directed graph
  • Check for Bipartite graph
  • Unit Area of Largest region of 1s
• Hard
  • Alien Dictionary
  • Word Ladder

Trie

• Medium
  • Minimum XOR value pair
  • Word Boggle – II
  • Most frequent word in an array of strings
  • Minimum XOR value pair

Greedy

• Medium
  • N meetings in one room
  • Coin Piles
  • Maximize Toys
  • Largest number with given sum
  • Minimize the heights
  • Fractional Knapsack
  • Job Sequencing
  • Police and Thieves
  • Water the Plants

  DP

  • Easy 
    • Count ways to reach the n’th stair
    • Get Minimum Squares
    • Nth Fibonacci Number
  • Medium
    • 0 – 1 Knapsack Problem
    • Number of Coins
    • Edit distance
    • Maximize The Cut Segments
    • Box Stacking
    • Longest Increasing Subsequence
    • Longest Palindromic Substring
    • Longest Common Substring
    • Longest Common Subsequence
    • Wildcard Pattern Matching
    • Total Decoding Messages
    • Max length chain
    • Maximum sum increasing subsequence
    • Minimum number of jumps
    • Subset Sum Problem
    • Maximum path sum in matrix
    • Player with max score
    • Shortest Common Supersequence
    • Palindrome Partitioning
    • Form a Palindrome
  • Hard
    • Boolean Parenthesization
    • Matrix Chain
    • Maximum Profit
    • Minimum Cost Path
    • Partition Equal Subset Sum

  Recursion

  • Easy
    • Number of Paths
    • Pascals Triangle
    • Josephus problem
    • Tower of Hanoi
  • Medium
    • Special Keyboard
    • Flood Fill Algorithm

  Backtracking

  • Easy
    • Permutations    
  • Medium
    • Letter Combinations of a Phone Number
    • Generate Parentheses
    • Word Boggle – 1
    • Rat in a Maze Problem
    • Largest number in K swaps
    • Combination Sum
  • Hard
    • Palindrome Partitioning
    • N-Queen Problem
    • Solve the Sudoku

  Algorithms

  • Easy
    • Bubble Sort
    • Insertion Sort
    • Selection Sort
  • Medium
    • Merge Sort
    • Quick Sort
    • Heap Sort
    • Count Sort
    • Kadane Algorithm
    • Minimum Spanning Tree
    • Implementing Dijkstra Algorithm
    • Floyd Warshall
    • Bellman Ford Algorithm
    • Rabin-Karp Algorithm
    • KMP algorithm
    • Z Algorithm
    • Huffman Encoding

  Design

  • Easy
    • Stack using two queues
    • Queue using stack
  • Medium
    • Ternary Search
    • Binary Heap Operations
    • LRU cache
    • Trie | (Insert and Search)

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