ServiceNow Coding Interview Questions

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...

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.

Group Anagrams

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

Valid Parentheses

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

LRU Cache

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

Find Minimum Diameter After Merging Two Trees

There exist two undirected trees with n and m nodes, numbered from 0 to n - 1 and from 0 to m - 1, respectively. You are given two 2D integer arrays edges1 and...

Lexicographically Smallest String After Operations With Constraint

You are given a string s and an integer k.

Generate Parentheses

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

Number of Distinct Roll Sequences

You are given an integer n. You roll a fair 6-sided dice n times. Determine the total number of distinct sequences of rolls possible such that the following con...

Longest Substring Without Repeating Characters

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

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.

Design HashMap

Design a HashMap without using any built-in hash table libraries.

Move Zeroes

Given an integer array nums, move all 0's to the end of it while maintaining the relative order of the non-zero elements.

Zigzag Conversion

The string "PAYPALISHIRING" is written in a zigzag pattern on a given number of rows like this: (you may want to display this pattern in a fixed font for better...

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...

Two Sum

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

Daily Temperatures

Given an array of integers temperatures represents the daily temperatures, return an array answer such that answer[i] is the number of days you have to wait aft...

First Missing Positive

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

Kth Largest Element in an Array

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

Container With Most Water

You are given an integer array height of length n. There are n vertical lines drawn such that the two endpoints of the ith line are (i, 0) and (i, height[i]).

Maximal Square

Given an m x n binary matrix filled with 0's and 1's, find the largest square containing only 1's and return its area.

String Compression

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

Validate Binary Search Tree

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

Longest Palindromic Substring

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

Pacific Atlantic Water Flow

There is an m x n rectangular island that borders both the Pacific Ocean and Atlantic Ocean. The Pacific Ocean touches the island's left and top edges, and the...

LFU Cache

Design and implement a data structure for a Least Frequently Used (LFU) cache.

Top K Frequent Words

Given an array of strings words and an integer k, return the k most frequent strings.

Maximum Product Subarray

Given an integer array nums, find a subarray that has the largest product, and return the product.

Number of Islands

Given an m x n 2D binary grid grid which represents a map of '1's (land) and '0's (water), return the number of islands.

Reverse Linked List

Given the head of a singly linked list, reverse the list, and return the reversed list.

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.

Search in Rotated Sorted Array

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

Set Matrix Zeroes

Given an m x n integer matrix matrix, if an element is 0, set its entire row and column to 0's.

Maximum Subarray

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

Largest Number

Given a list of non-negative integers nums, arrange them such that they form the largest number and return it.

Binary Tree Right Side View

Given the root of a binary tree, imagine yourself standing on the right side of it, return the values of the nodes you can see ordered from top to bottom.

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...

Fraction to Recurring Decimal

Given two integers representing the numerator and denominator of a fraction, return the fraction in string format.

Valid Parenthesis String

Given a string s containing only three types of characters: '(', ')' and '', return true if s is valid.

Longest Consecutive Sequence

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

Validate IP Address

Given a string queryIP, return "IPv4" if IP is a valid IPv4 address, "IPv6" if IP is a valid IPv6 address or "Neither" if IP is not a correct IP of any type.

Number of Visible People in a Queue

There are n people standing in a queue, and they numbered from 0 to n - 1 in left to right order. You are given an array heights of distinct integers where heig...

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.

Sum Root to Leaf Numbers

You are given the root of a binary tree containing digits from 0 to 9 only.

Vowels of All Substrings

Given a string word, return the sum of the number of vowels ('a', 'e', 'i', 'o', and 'u') in every substring of word.

Basic Calculator II

Given a string s which represents an expression, evaluate this expression and return its value.

Minimum Number of Taps to Open to Water a Garden

There is a one-dimensional garden on the x-axis. The garden starts at the point 0 and ends at the point n. (i.e., the length of the garden is n).

Rotting Oranges

You are given an m x n grid where each cell can have one of three values:

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...

Target Sum

You are given an integer array nums and an integer target.

Search Suggestions System

You are given an array of strings products and a string searchWord.

Next Permutation

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

Coin Change

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

Rotate Array

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

Find First and Last Position of Element in Sorted Array

Given an array of integers nums sorted in non-decreasing order, find the starting and ending position of a given target value.

Implement Trie (Prefix Tree)

A trie (pronounced as "try") or prefix tree is a tree data structure used to efficiently store and retrieve keys in a dataset of strings. There are various appl...

Single Element in a Sorted Array

You are given a sorted array consisting of only integers where every element appears exactly twice, except for one element which appears exactly once.

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...

Sliding Window Maximum

You are given an array of integers nums, there is a sliding window of size k which is moving from the very left of the array to the very right. You can only see...

Gas Station

There are n gas stations along a circular route, where the amount of gas at the ith station is gas[i].

Palindrome Linked List

Given the head of a singly linked list, return true if it is a palindrome or 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.

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:

Find Peak Element

A peak element is an element that is strictly greater than its neighbors.

Populating Next Right Pointers in Each Node

You are given a perfect binary tree where all leaves are on the same level, and every parent has two children. The binary tree has the following definition:

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.

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...

Word Break II

Given a string s and a dictionary of strings wordDict, add spaces in s to construct a sentence where each word is a valid dictionary word. Return all such possi...

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...

Amount of Time for Binary Tree to Be Infected

You are given the root of a binary tree with unique values, and an integer start. At minute 0, an infection starts from the node with value start.

Check if a Parentheses String Can Be Valid

A parentheses string is a non-empty string consisting only of '(' and ')'. It is valid if any of the following conditions is true:

Minimum One Bit Operations to Make Integers Zero

Given an integer n, you must transform it into 0 using the following operations any number of times:

Binary Tree Zigzag Level Order Traversal

Given the root of a binary tree, return the zigzag level order traversal of its nodes' values. (i.e., from left to right, then right to left for the next level...

4Sum

Given an array nums of n integers, return an array of all the unique quadruplets [nums[a], nums[b], nums[c], nums[d]] such that:

Permutations

Given an array nums of distinct integers, return all the possible permutations. You can return the answer in any order.

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.

Combination Sum

Given an array of distinct integers candidates and a target integer target, return a list of all unique combinations of candidates where the chosen numbers sum...

Jump Game

You are given an integer array nums. You are initially positioned at the array's first index, and each element in the array represents your maximum jump length...

Pow(x, n)

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

Time Needed to Rearrange a Binary String

You are given a binary string s. In one second, all occurrences of "01" are simultaneously replaced with "10". This process repeats until no occurrences of "01"...