DoorDash Coding Interview Questions

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...

Longest Increasing Path in a Matrix

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

Maximum Profit in Job Scheduling

We have n jobs, where every job is scheduled to be done from startTime[i] to endTime[i], obtaining a profit of profit[i].

Search Suggestions System

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

Koko Eating Bananas

Koko loves to eat bananas. There are n piles of bananas, the ith pile has piles[i] bananas. The guards have gone and will come back in h hours.

Most Profit Assigning Work

You have n jobs and m workers. You are given three arrays: difficulty, profit, and worker where:

Check if One String Swap Can Make Strings Equal

You are given two strings s1 and s2 of equal length. A string swap is an operation where you choose two indices in a string (not necessarily different) and swap...

Minimum Number of Steps to Make Two Strings Anagram

You are given two strings of the same length s and t. In one step you can choose any character of t and replace it with another character.

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​​...

Find K Closest Elements

Given a sorted integer array arr, two integers k and x, return the k closest integers to x in the array. The result should also be sorted in ascending order.

Buddy Strings

Given two strings s and goal, return true if you can swap two letters in s so the result is equal to goal, otherwise, return false.

Next Greater Element III

Given a positive integer n, find the smallest integer which has exactly the same digits existing in the integer n and is greater in value than n. If no such pos...

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.

Find Nearest Point That Has the Same X or Y Coordinate

You are given two integers, x and y, which represent your current location on a Cartesian grid: (x, y). You are also given an array points where each points[i]...

Count Sub Islands

You are given two m x n binary matrices grid1 and grid2 containing only 0's (representing water) and 1's (representing land). An island is a group of 1's connec...

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...

Count Nodes With the Highest Score

There is a binary tree rooted at 0 consisting of n nodes. The nodes are labeled from 0 to n - 1. You are given a 0-indexed integer array parents representing th...

Serialize and Deserialize Binary Tree

Serialization is the process of converting a data structure or object into a sequence of bits so that it can be stored in a file or memory buffer, or transmitte...

Basic Calculator II

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

Count All Valid Pickup and Delivery Options

Given n orders, each order consists of a pickup and a delivery service.

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...

Vertical Order Traversal of a Binary Tree

Given the root of a binary tree, calculate the vertical order traversal of the binary tree.

Two Sum

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

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...

Immediate Food Delivery II

Table: Delivery

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...

Interval List Intersections

You are given two lists of closed intervals, firstList and secondList, where firstList[i] = [starti, endi] and secondList[j] = [startj, endj]. Each list of inte...

Mice and Cheese

There are two mice and n different types of cheese, each type of cheese should be eaten by exactly one mouse.

Subsequence With the Minimum Score

You are given two strings s and t.

Basic Calculator

Given a string s representing a valid expression, implement a basic calculator to evaluate it, and return the result of the evaluation.

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....

Largest Rectangle in Histogram

Given an array of integers heights representing the histogram's bar height where the width of each bar is 1, return the area of the largest rectangle in the his...

01 Matrix

Given an m x n binary matrix mat, return the distance of the nearest 0 for each cell.

Next Permutation

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

Max Area of Island

You are given an m x n binary matrix grid. An island is a group of 1's (representing land) connected 4-directionally (horizontal or vertical.) You may assume al...

Word Search II

Given an m x n board of characters and a list of strings words, return all words on the board.

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...

Minimum Size Subarray Sum

Given an array of positive integers nums and a positive integer target, return the minimal length of a subarray whose sum is greater than or equal to target. If...

Longest Common Subsequence

Given two strings text1 and text2, return the length of their longest common subsequence. If there is no common subsequence, return 0.

Swim in Rising Water

You are given an n x n integer matrix grid where each value grid[i][j] represents the elevation at that point (i, j).

Design Add and Search Words Data Structure

Design a data structure that supports adding new words and finding if a string matches any previously added string.

Jump Game II

You are given a 0-indexed array of integers nums of length n. You are initially positioned at index 0.

Sudoku Solver

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

Ways to Make a Fair Array

You are given an integer array nums. You can choose exactly one index (0-indexed) and remove the element. Notice that the index of the elements may change after...

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.

LRU Cache

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

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...

Sliding Window Median

The median is the middle value in an ordered integer list. If the size of the list is even, there is no middle value. So the median is the mean of the two middl...

Minimize Malware Spread

You are given a network of n nodes represented as an n x n adjacency matrix graph, where the ith node is directly connected to the jth node if graph[i][j] == 1.

Maximum Gap

Given an integer array nums, return the maximum difference between two successive elements in its sorted form. If the array contains less than two elements, ret...

Number of Provinces

There are n cities. Some of them are connected, while some are not. If city a is connected directly with city b, and city b is connected directly with city c, t...

Maximum Path Quality of a Graph

There is an undirected graph with n nodes numbered from 0 to n - 1 (inclusive). You are given a 0-indexed integer array values where values[i] is the value of t...

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:

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...

Capacity To Ship Packages Within D Days

A conveyor belt has packages that must be shipped from one port to another within days days.

LFU Cache

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

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...

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.

Task Scheduler II

You are given a 0-indexed array of positive integers tasks, representing tasks that need to be completed in order, where tasks[i] represents the type of the ith...

K-Similar Strings

Strings s1 and s2 are k-similar (for some non-negative integer k) if we can swap the positions of two letters in s1 exactly k times so that the resulting string...

Similar String Groups

Two strings, X and Y, are considered similar if either they are identical or we can make them equivalent by swapping at most two letters (in distinct positions)...

Counting Words With a Given Prefix

You are given an array of strings words and a string pref.

Number of Closed Islands

Given a 2D grid consists of 0s (land) and 1s (water). An island is a maximal 4-directionally connected group of 0s and a closed island is an island totally (all...

Maximum Performance of a Team

You are given two integers n and k and two integer arrays speed and efficiency both of length n. There are n engineers numbered from 1 to n. speed[i] and effici...

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:

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.

Path Sum II

Given the root of a binary tree and an integer targetSum, return all root-to-leaf paths where the sum of the node values in the path equals targetSum. Each path...

Range Sum Query 2D - Immutable

Given a 2D matrix matrix, handle multiple queries of the following type:

Insert Delete GetRandom O(1)

Implement the RandomizedSet class:

Merge k Sorted Lists

You are given an array of k linked-lists lists, each linked-list is sorted in ascending order.