EPAM Systems Coding Interview Questions

Longest Substring Without Repeating Characters

Given a string s, find the length of the longest substring without duplicate characters.

Valid Parentheses

Given a string s containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid.

Two Sum

Given an array of integers nums and an integer target, return the indices of the two numbers that add up to target.

Minimum Operations to Make a Uni-Value Grid

You are given a 2D integer grid of size m x n and an integer x. In one operation, you can add x to or subtract x from any element in the grid.

Group Anagrams

Given an array of strings strs, group the anagrams together. You can return the answer in any order.

Longest Palindromic Substring

Given a string s, return the longest palindromic substring in s.

Longest Common Prefix

Write a function to find the longest common prefix string amongst an array of strings.

Valid Anagram

Given two strings s and t, return true if t is an anagram of s, and false otherwise.

Merge Sorted Array

You are given two integer arrays nums1 and nums2, sorted in non-decreasing order, and two integers m and n, representing the number of elements in nums1 and num...

Valid Palindrome

A phrase is a palindrome if, after converting all uppercase letters into lowercase letters and removing all non-alphanumeric characters, it reads the same forwa...

Best Time to Buy and Sell Stock

You are given an array prices where prices[i] is the price of a given stock on the ith day.

Two Sum II - Input Array Is Sorted

Given a 1-indexed array of integers numbers that is already sorted in non-decreasing order, find two numbers such that they add up to a specific target number....

Palindrome Number

Given an integer x, return true if x is a palindrome, and false otherwise.

3Sum

Given an integer array nums, return all the triplets [nums[i], nums[j], nums[k]] such that i != j, i != k, and j != k, and nums[i] + nums[j] + nums[k] == 0.

Trapping Rain Water

Given n non-negative integers representing an elevation map where the width of each bar is 1, compute how much water it can trap after raining.

Pow(x, n)

Implement pow(x, n), which calculates x raised to the power n (i.e., xn).

Merge Two Sorted Lists

You are given the heads of two sorted linked lists list1 and list2.

Reverse String

Write a function that reverses a string. The input string is given as an array of characters s.

Maximum Difference Between Node and Ancestor

Given the root of a binary tree, find the maximum value v for which there exist different nodes a and b where v = |a.val - b.val| and a is an ancestor of b.

Managers with at Least 5 Direct Reports

Table: Employee

First Unique Character in a String

Given a string s, find the first non-repeating character in it and return its index. If it does not exist, return -1.

Partition Equal Subset Sum

Given an integer array nums, return true if you can partition the array into two subsets such that the sum of the elements in both subsets is equal or false oth...

Running Sum of 1d Array

Given an array nums. We define a running sum of an array as runningSum[i] = sum(nums[0]…nums[i]).

Duplicate Emails

Table: Person

To Be Or Not To Be

Write a function expect that helps developers test their code. It should take in any value val and return an object with the following two functions.

Kth Largest Element in an Array

Given an integer array nums and an integer k, return the kth largest element in the array.

Merge Intervals

Given an array of intervals where intervals[i] = [starti, endi], merge all overlapping intervals, and return an array of the non-overlapping intervals that cove...

Rotate Array

Given an integer array nums, rotate the array to the right by k steps, where k is non-negative.

Reverse Integer

Given a signed 32-bit integer x, return x with its digits reversed. If reversing x causes the value to go outside the signed 32-bit integer range [-231, 231 - 1...

Add Two Numbers

You are given two non-empty linked lists representing two non-negative integers. The digits are stored in reverse order, and each of their nodes contains a sing...

House Robber

You are a professional robber planning to rob houses along a street. Each house has a certain amount of money stashed, the only constraint stopping you from rob...

Coin Change

You are given an integer array coins representing coins of different denominations and an integer amount representing a total amount of money.

Ugly Number II

An ugly number is a positive integer whose prime factors are limited to 2, 3, and 5.

Binary Search

Given an array of integers nums which is sorted in ascending order, and an integer target, write a function to search target in nums. If target exists, then ret...

Search in Rotated Sorted Array

There is an integer array nums sorted in ascending order (with distinct values).

Asteroid Collision

We are given an array asteroids of integers representing asteroids in a row. The indices of the asteroid in the array represent their relative position in space...

First Missing Positive

Given an unsorted integer array nums. Return the smallest positive integer that is not present in nums.

Reverse Linked List II

Given the head of a singly linked list and two integers left and right where left <= right, reverse the nodes of the list from position left to position right,...

String Compression

Given an array of characters chars, compress it using the following algorithm:

Longest Consecutive Sequence

Given an unsorted array of integers nums, return the length of the longest consecutive elements sequence.

Top K Frequent Elements

Given an integer array nums and an integer k, return the k most frequent elements. You may return the answer in any order.

Linked List Cycle

Given head, the head of a linked list, determine if the linked list has a cycle in it.

Isomorphic Strings

Given two strings s and t, determine if they are isomorphic.