IBM Coding Interview Questions

Exclusive Time of Functions

On a single-threaded CPU, we execute a program containing n functions. Each function has a unique ID between 0 and n-1.

Integer to Roman

Seven different symbols represent Roman numerals with the following values:

Fizz Buzz

Given an integer n, return a string array answer (1-indexed) where:

Roman to Integer

Roman numerals are represented by seven different symbols: I, V, X, L, C, D and M.

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

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

Count Ways to Group Overlapping Ranges

You are given a 2D integer array ranges where ranges[i] = [starti, endi] denotes that all integers between starti and endi (both inclusive) are contained in the...

Minimum Operations to Make All Array Elements Equal

You are given an array nums consisting of positive integers.

Rotate Image

You are given an n x n 2D matrix representing an image, rotate the image by 90 degrees (clockwise).

Minimum Absolute Difference

Given an array of distinct integers arr, find all pairs of elements with the minimum absolute difference of any two elements.

Minimum Operations to Make Median of Array Equal to K

You are given an integer array nums and a non-negative integer k. In one operation, you can increase or decrease any element by 1.

Find The First Player to win K Games in a Row

A competition consists of n players numbered from 0 to n - 1.

The kth Factor of n

You are given two positive integers n and k. A factor of an integer n is defined as an integer i where n % i == 0.

Average Value of Even Numbers That Are Divisible by Three

Given an integer array nums of positive integers, return the average value of all even integers that are divisible by 3.

Longest Substring Without Repeating Characters

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

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...

String Compression

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

Count Vowel Strings in Ranges

You are given a 0-indexed array of strings words and a 2D array of integers queries.

Count the Number of Incremovable Subarrays II

You are given a 0-indexed array of positive integers nums.

Minimum Levels to Gain More Points

You are given a binary array possible of length n.

Sort the Students by Their Kth Score

There is a class with m students and n exams. You are given a 0-indexed m x n integer matrix score, where each row represents one student and score[i][j] denote...

Minimum Length of String After Operations

You are given a string s.

Find Products of Elements of Big Array

The powerful array of a non-negative integer x is defined as the shortest sorted array of powers of two that sum up to x. The table below illustrates examples o...

Type of Triangle

You are given a 0-indexed integer array nums of size 3 which can form the sides of a triangle.

Taking Maximum Energy From the Mystic Dungeon

In a mystic dungeon, n magicians are standing in a line. Each magician has an attribute that gives you energy. Some magicians can give you negative energy, whic...

Find Occurrences of an Element in an Array

You are given an integer array nums, an integer array queries, and an integer x.

Find the Array Concatenation Value

You are given a 0-indexed integer array nums.

Maximum Units on a Truck

You are assigned to put some amount of boxes onto one truck. You are given a 2D array boxTypes, where boxTypes[i] = [numberOfBoxesi, numberOfUnitsPerBoxi]:

Longest Common Prefix

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

Count Binary Substrings

Given a binary string s, return the number of non-empty substrings that have the same number of 0's and 1's, and all the 0's and all the 1's in these substrings...

Get Equal Substrings Within Budget

You are given two strings s and t of the same length and an integer maxCost.

Valid Parentheses

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

Letter Combinations of a Phone Number

Given a string containing digits from 2-9 inclusive, return all possible letter combinations that the number could represent. Return the answer in any order.

Minimum Suffix Flips

You are given a 0-indexed binary string target of length n. You have another binary string s of length n that is initially set to all zeros. You want to make s...

Numbers With Repeated Digits

Given an integer n, return the number of positive integers in the range [1, n] that have at least one repeated digit.

Maximum Sum of Distinct Subarrays With Length K

You are given an integer array nums and an integer k. Find the maximum subarray sum of all the subarrays of nums that meet the following conditions:

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...

Longest Palindromic Substring

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

Lexicographically Smallest String After Substring Operation

Given a string s consisting of lowercase English letters. Perform the following operation:

Longest Consecutive Sequence

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

Spiral Matrix

Given an m x n matrix, return all elements of the matrix in spiral order.

Shortest and Lexicographically Smallest Beautiful String

You are given a binary string s and a positive integer k.

Count Pairs Of Similar Strings

You are given a 0-indexed string array words.

Maximum Subarray

Given an integer array nums, find the subarray with the largest sum, and return its sum.

Divide Players Into Teams of Equal Skill

You are given a positive integer array skill of even length n where skill[i] denotes the skill of the ith player. Divide the players into n / 2 teams of size 2...

Group Anagrams

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

Subarray Product Less Than K

Given an array of integers nums and an integer k, return the number of contiguous subarrays where the product of all the elements in the subarray is strictly le...

Minimum Swaps to Group All 1's Together II

A swap is defined as taking two distinct positions in an array and swapping the values in them.

Climbing Stairs

You are climbing a staircase. It takes n steps to reach the top.

Smallest Missing Non-negative Integer After Operations

You are given a 0-indexed integer array nums and an integer value.

Validate Binary Search Tree

Given the root of a binary tree, determine if it is a valid binary search tree (BST).

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.

Backspace String Compare

Given two strings s and t, return true if they are equal when both are typed into empty text editors. '' means a backspace character.

Number of Operations to Make Network Connected

There are n computers numbered from 0 to n - 1 connected by ethernet cables connections forming a network where connections[i] = [ai, bi] represents a connectio...

Rotate Array

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

Intersection of Two Arrays

Given two integer arrays nums1 and nums2, return an array of their intersection. Each element in the result must be unique and you may return the result in any...

Find Minimum in Rotated Sorted Array

Suppose an array of length n sorted in ascending order is rotated between 1 and n times. For example, the array nums = [0,1,2,4,5,6,7] might become:

Odd String Difference

You are given an array of equal-length strings words. Assume that the length of each string is n.

Single-Threaded CPU

You are given n​​​​​​ tasks labeled from 0 to n - 1 represented by a 2D integer array tasks, where tasks[i] = [enqueueTimei, processingTimei] means that the i​​...

Palindrome Number

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

Subarray Sum Equals K

Given an array of integers nums and an integer k, return the total number of subarrays whose sum equals to k.

Flipping an Image

Given an n x n binary matrix image, flip the image horizontally, then invert it, and return the resulting image.

Flip String to Monotone Increasing

A binary string is monotone increasing if it consists of some number of 0's (possibly none), followed by some number of 1's (also possibly none).

Find The Original Array of Prefix Xor

You are given an integer array pref of size n. Find and return the array arr of size n that satisfies:

Product of Array Except Self

Given an integer array nums, return an array answer such that answer[i] is equal to the product of all the elements of nums except nums[i].

Longest Increasing Subsequence

Given an integer array nums, return the length of the longest strictly increasing subsequence.

Next Permutation

A permutation of an array of integers is an arrangement of its members into a sequence or linear order.

Find the Index of the First Occurrence in a String

Given two strings needle and haystack, return the index of the first occurrence of needle in haystack, or -1 if needle is not part of haystack.

Median of Two Sorted Arrays

Given two sorted arrays nums1 and nums2 of size m and n respectively, return the median of the two sorted arrays.

Subsets

Given an integer array nums of unique elements, return all possible subsets (the power set).

Generate Parentheses

Given n pairs of parentheses, write a function to generate all combinations of well-formed parentheses.

Range Product Queries of Powers

Given a positive integer n, there exists a 0-indexed array called powers, composed of the minimum number of powers of 2 that sum to n. The array is sorted in no...

N-Queens

The n-queens puzzle is the problem of placing n queens on an n x n chessboard such that no two queens attack each other.

Find All Possible Stable Binary Arrays II

You are given 3 positive integers zero, one, and limit.

Removing Stars From a String

You are given a string s, which contains stars .

Minimum Number of Flips to Make the Binary String Alternating

You are given a binary string s. You are allowed to perform two types of operations on the string in any sequence:

Rearrange Array to Maximize Prefix Score

You are given a 0-indexed integer array nums. You can rearrange the elements of nums to any order (including the given order).

132 Pattern

Given an array of n integers nums, a 132 pattern is a subsequence of three integers nums[i], nums[j] and nums[k] such that i < j < k and nums[i] < nums[k] < num...

The Employee That Worked on the Longest Task

There are n employees, each with a unique id from 0 to n - 1.

Count Number of Teams

There are n soldiers standing in a line. Each soldier is assigned a unique rating value.

Minimum Operations to Reduce an Integer to 0

You are given a positive integer n, you can do the following operation any number of times:

Prime In Diagonal

You are given a 0-indexed two-dimensional integer array nums.

Majority Element

Given an array nums of size n, return the majority element.

Find the Duplicate Number

Given an array of integers nums containing n + 1 integers where each integer is in the range [1, n] inclusive.

Least Number of Unique Integers after K Removals

Given an array of integers arr and an integer k. Find the least number of unique integers after removing exactly k elements.

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...

Task Scheduler

You are given an array of CPU tasks, each labeled with a letter from A to Z, and a number n. Each CPU interval can be idle or allow the completion of one task....

Increasing Triplet Subsequence

Given an integer array nums, return true if there exists a triple of indices (i, j, k) such that i < j < k and nums[i] < nums[j] < nums[k]. If no such indices e...

Maximum Number of Tasks You Can Assign

You have n tasks and m workers. Each task has a strength requirement stored in a 0-indexed integer array tasks, with the ith task requiring tasks[i] strength to...

Degree of an Array

Given a non-empty array of non-negative integers nums, the degree of this array is defined as the maximum frequency of any one of its elements.

Word Break

Given a string s and a dictionary of strings wordDict, return true if s can be segmented into a space-separated sequence of one or more dictionary words.

Happy Number

Write an algorithm to determine if a number n is happy.

LRU Cache

Design a data structure that follows the constraints of a Least Recently Used (LRU) cache.