Snap Coding Interview Questions

LRU Cache

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

Minimum Window Substring

Given two strings s and t of lengths m and n respectively, return the minimum window substring of s such that every character in t (including duplicates) is inc...

Word Ladder

A transformation sequence from word beginWord to word endWord using a dictionary wordList is a sequence of words beginWord -> s1 -> s2 -> ... -> sk such that:

Making A Large Island

You are given an n x n binary matrix grid. You are allowed to change at most one 0 to be 1.

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...

Course Schedule II

There are a total of numCourses courses you have to take, labeled from 0 to numCourses - 1. You are given an array prerequisites where prerequisites[i] = [ai, b...

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.

Bus Routes

You are given an array routes representing bus routes where routes[i] is a bus route that the ith bus repeats forever.

Valid Sudoku

Determine if a 9 x 9 Sudoku board is valid. Only the filled cells need to be validated according to the following rules:

Min Stack

Design a stack that supports push, pop, top, and retrieving the minimum element in constant time.

Power of Two

Given an integer n, return true if it is a power of two. Otherwise, return false.

Combination Sum II

Given a collection of candidate numbers (candidates) and a target number (target), find all unique combinations in candidates where the candidate numbers sum to...

Frog Jump

A frog is crossing a river. The river is divided into some number of units, and at each unit, there may or may not exist a stone. The frog can jump on a stone,...

Wildcard Matching

Given an input string (s) and a pattern (p), implement wildcard pattern matching with support for '?' and '' where:

Sudoku Solver

Write a program to solve a Sudoku puzzle by filling the empty cells.

Burst Balloons

You are given n balloons, indexed from 0 to n - 1. Each balloon is painted with a number on it represented by an array nums. You are asked to burst all the ball...

Bricks Falling When Hit

You are given an m x n binary grid, where each 1 represents a brick and 0 represents an empty space. A brick is stable if:

Least Operators to Express Number

Given a single positive integer x, we will write an expression of the form x (op1) x (op2) x (op3) x ... where each operator op1, op2, etc. is either addition,...

Combination Sum IV

Given an array of distinct integers nums and a target integer target, return the number of possible combinations that add up to target.

Largest Merge Of Two Strings

You are given two strings word1 and word2. You want to construct a string merge in the following way: while either word1 or word2 are non-empty, choose one of t...

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...

Unique Binary Search Trees

Given an integer n, return the number of structurally unique BST's (binary search trees) which has exactly n nodes of unique values from 1 to n.

String Compression

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

Reverse Words in a String

Given an input string s, reverse the order of the words.

Game of Life

According to Wikipedia's article: "The Game of Life, also known simply as Life, is a cellular automaton devised by the British mathematician John Horton Conway...

Reverse Linked List

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

Remove K Digits

Given string num representing a non-negative integer num, and an integer k, return the smallest possible integer after removing k digits from num.

Basic Calculator II

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

Shortest Path in a Grid with Obstacles Elimination

You are given an m x n integer matrix grid where each cell is either 0 (empty) or 1 (obstacle). You can move up, down, left, or right from and to an empty cell...

Cheapest Flights Within K Stops

There are n cities connected by some number of flights. You are given an array flights where flights[i] = [fromi, toi, pricei] indicates that there is a flight...

Word Search

Given an m x n grid of characters board and a string word, return true if word exists in the grid.

Decode Ways

You have intercepted a secret message encoded as a string of numbers. The message is decoded via the following mapping:

Valid Arrangement of Pairs

You are given a 0-indexed 2D integer array pairs where pairs[i] = [starti, endi]. An arrangement of pairs is valid if for every index i where 1 <= i < pairs.len...

Best Time to Buy and Sell Stock III

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

Design a Text Editor

Design a text editor with a cursor that can do the following:

Score of Parentheses

Given a balanced parentheses string s, return the score of the string.

Minimum Time to Complete All Tasks

There is a computer that can run an unlimited number of tasks at the same time. You are given a 2D integer array tasks where tasks[i] = [starti, endi, durationi...

Evaluate Division

You are given an array of variable pairs equations and an array of real numbers values, where equations[i] = [Ai, Bi] and values[i] represent the equation Ai /...

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.

Insert Delete GetRandom O(1)

Implement the RandomizedSet class:

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...

Parallel Courses III

You are given an integer n, which indicates that there are n courses labeled from 1 to n. You are also given a 2D integer array relations where relations[j] = [...

Reconstruct Itinerary

You are given a list of airline tickets where tickets[i] = [fromi, toi] represent the departure and the arrival airports of one flight. Reconstruct the itinerar...

Binary Tree Maximum Path Sum

A path in a binary tree is a sequence of nodes where each pair of adjacent nodes in the sequence has an edge connecting them. A node can only appear in the sequ...

Accounts Merge

Given a list of accounts where each element accounts[i] is a list of strings, where the first element accounts[i][0] is a name, and the rest of the elements are...

Shortest Bridge

You are given an n x n binary matrix grid where 1 represents land and 0 represents water.

Course Schedule

There are a total of numCourses courses you have to take, labeled from 0 to numCourses - 1. You are given an array prerequisites where prerequisites[i] = [ai, b...

Max Consecutive Ones III

Given a binary array nums and an integer k, return the maximum number of consecutive 1's in the array if you can flip at most k 0's.

Group Anagrams

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

Merge Two Sorted Lists

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

Minimum Remove to Make Valid Parentheses

Given a string s of '(' , ')' and lowercase English characters.

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.

K Closest Points to Origin

Given an array of points where points[i] = [xi, yi] represents a point on the X-Y plane and an integer k, return the k closest points to the origin (0, 0).

Find Peak Element

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

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].

Edit Distance

Given two strings word1 and word2, return the minimum number of operations required to convert word1 to word2.

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.

Jump Game III

Given an array of non-negative integers arr, you are initially positioned at start index of the array. When you are at index i, you can jump to i + arr[i] or i...

Custom Sort String

You are given two strings order and s. All the characters of order are unique and were sorted in some custom order previously.

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.

Maximum Subarray

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

Search a 2D Matrix

You are given an m x n integer matrix matrix with the following two properties:

Search Suggestions System

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

Longest String Chain

You are given an array of words where each word consists of lowercase English letters.

Car Fleet

There are n cars at given miles away from the starting mile 0, traveling to reach the mile target.

Minimum Number of Refueling Stops

A car travels from a starting position to a destination which is target miles east of the starting position.

Knight Dialer

The chess knight has a unique movement, it may move two squares vertically and one square horizontally, or two squares horizontally and one square vertically (w...

Search a 2D Matrix II

Write an efficient algorithm that searches for a value target in an m x n integer matrix matrix. This matrix has the following properties:

Minimum Area Rectangle

You are given an array of points in the X-Y plane points where points[i] = [xi, yi].

Design Browser History

You have a browser of one tab where you start on the homepage and you can visit another url, get back in the history number of steps or move forward in the hist...

Longest Increasing Path in a Matrix

Given an m x n integers matrix, return the length of the longest increasing path in matrix.

Complement of Base 10 Integer

The complement of an integer is the integer you get when you flip all the 0's to 1's and all the 1's to 0's in its binary representation.

Random Pick with Weight

You are given a 0-indexed array of positive integers w where w[i] describes the weight of the ith index.

Minimum Cost For Tickets

You have planned some train traveling one year in advance. The days of the year in which you will travel are given as an integer array days. Each day is an inte...

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).

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.

Maximum Frequency Stack

Design a stack-like data structure to push elements to the stack and pop the most frequent element from the stack.

Minimize Result by Adding Parentheses to Expression

You are given a 0-indexed string expression of the form "<num1>+<num2>" where <num1> and <num2> represent positive integers.

Maximize Distance to Closest Person

You are given an array representing a row of seats where seats[i] = 1 represents a person sitting in the ith seat, and seats[i] = 0 represents that the ith seat...

Movie Rating

Table: Movies

Verifying an Alien Dictionary

In an alien language, surprisingly, they also use English lowercase letters, but possibly in a different order. The order of the alphabet is some permutation of...

Reorder Data in Log Files

You are given an array of logs. Each log is a space-delimited string of words, where the first word is the identifier.

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.