Top 50 Hash Data Structure Problems for Programming Interviews

Hash Data Structure uses a hash function to store data like a smart storage system. This article covers the most important and common problems. We have covered all the ranges from easy-level problems to hard-level problems. Hash is like this article a well-organized filing cabinet where you can get the store for finding things super quickly.

Here are the top 50 problems that take you forward in Data Structures and Algorithms from basic to advanced!

Easy Problems

• Find the count of distinct elements in an array
• Minimum insertions to form a palindrome with permutations allowed
• Find whether an array is a subset of another array
• Find the frequency of each character in a string
• find the first non-repeating character from a stream of characters
• Count number of Distinct Substring in a String
• print all unique words of a string
• Count all distinct pairs with difference equal to k
• Minimum number of elements that should be removed to make the array good
• Find the intersection of two arrays
• Find missing elements of a range
• Find the pair with given sum in an array
• Find the only repetitive element between 1 to n-1
• Remove duplicates from an array

Intermediate Problems

• Group words with their anagrams
• Find all pairs (a, b) in an array such that a % b = k
• Count number of subsets having a particular XOR value
• Find the subarray with given sum in an array
• Largest subarray having sum greater than k
• Find the length of the longest consecutive sequence within numbers
• Find all pairs with a given sum in an array
• Longest Consecutive Subsequence
• Find the first repeating element in an array
• Find the majority element in an array
• All unique triplets that sum up to a given value
• Subarrays with K Different Integers
• Maximum possible difference of two subsets of an array
• Find the length of largest subarray with 0 sum
• Find Itinerary from a given list of tickets
• Largest length subarray with equal number of 0s and 1s
• Print all subarrays with 0 sum
• Sort an array according to the order defined by another array
• Range Queries for Frequencies of array elements
• Count subarrays having total distinct elements same as original array

Advanced Problems

• Palindrome Substring Queries
• Random Pick with Blacklist
• Find All Duplicate Subtrees
• Minimum Window Substring
• Bus Routes
• Longest subarray with sum divisible by k
• Count distinct elements in every window of size k
• Check if an array can be divided into pairs whose sum is divisible by k
• Maximum Frequency Stack
• Smallest window in a string containing all the characters of another string
• Find the longest substring with k unique characters
• Length of longest strict bitonic subsequence
• Count maximum points on same line
• Kth Largest Element in a Strea
• Transform One String to Another using Minimum Number of Given Operation
• Phone directory