LinkedIn Coding Interview Questions

All O`one Data Structure

Design a data structure to store the strings' count with the ability to return the strings with minimum and maximum counts.

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:

Maximum Subarray

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

Valid Parentheses

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

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.

Maximum Product Subarray

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

Can Place Flowers

You have a long flowerbed in which some of the plots are planted, and some are not. However, flowers cannot be planted in adjacent plots.

Search in Rotated Sorted Array

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

Pow(x, n)

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

Insert Delete GetRandom O(1)

Implement the RandomizedSet class:

Partition to K Equal Sum Subsets

Given an integer array nums and an integer k, return true if it is possible to divide this array into k non-empty subsets whose sums are all equal.

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.

Paint House

There is a row of n houses, where each house can be painted one of three colors: red, blue, or green. The cost of painting each house with a certain color is di...

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...

Graph Valid Tree

You have a graph of n nodes labeled from 0 to n - 1. You are given an integer n and a list of edges where edges[i] = [ai, bi] indicates that there is an undirec...

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...

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 Depth of Binary Tree

Given the root of a binary tree, return its maximum depth.

Kth Largest Element in an Array

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

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.

Lowest Common Ancestor of a Binary Tree

Given a binary tree, find the lowest common ancestor (LCA) of two given nodes in the tree.

Lowest Common Ancestor of a Binary Search Tree

Given a binary search tree (BST), find the lowest common ancestor (LCA) node of two given nodes in the BST.

Isomorphic Strings

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

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...

Symmetric Tree

Given the root of a binary tree, check whether it is a mirror of itself (i.e., symmetric around its center).

Valid Perfect Square

Given a positive integer num, return true if num is a perfect square or false otherwise.

Kth Smallest Product of Two Sorted Arrays

Given two sorted 0-indexed integer arrays nums1 and nums2 as well as an integer k, return the kth (1-based) smallest product of nums1[i] nums2[j] where 0 <= i <...

Valid Number

Given a string s, return whether s is a valid number.

Count Integers in Intervals

Given an empty set of intervals, implement a data structure that can:

Number of Connected Components in an Undirected Graph

You have a graph of n nodes. You are given an integer n and an array edges where edges[i] = [ai, bi] indicates that there is an edge between ai and bi in the gr...

Max Points on a Line

Given an array of points where points[i] = [xi, yi] represents a point on the X-Y plane, return the maximum number of points that lie on the same straight line.

Second Minimum Node In a Binary Tree

Given a non-empty special binary tree consisting of nodes with the non-negative value, where each node in this tree has exactly two or zero sub-node. If the nod...

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...

Repeated DNA Sequences

The DNA sequence is composed of a series of nucleotides abbreviated as 'A', 'C', 'G', and 'T'.

Evaluate Reverse Polish Notation

You are given an array of strings tokens that represents an arithmetic expression in a Reverse Polish Notation.

Longest Palindromic Subsequence

Given a string s, find the longest palindromic subsequence's length in s.

Can I Win

In the "100 game" two players take turns adding, to a running total, any integer from 1 to 10. The player who first causes the running total to reach or exceed...

Binary Tree Level Order Traversal

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

LRU Cache

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

Encode and Decode Strings

Design an algorithm to encode a list of strings to a single string. The encoded string is then decoded back to the original list of strings.

Merge Two Sorted Lists

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

Permutations

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

Permutations II

Given a collection of numbers, nums, that might contain duplicates, return all possible unique permutations in any order.

Flatten Nested List Iterator

You are given a nested list of integers nestedList. Each element is either an integer or a list whose elements may also be integers or other lists. Implement an...

Two Sum

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

Find K Pairs with Smallest Sums

You are given two integer arrays nums1 and nums2 sorted in non-decreasing order and an integer k.

Merge k Sorted Lists

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

Palindromic Substrings

Given a string s, return the number of palindromic substrings in it.

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...

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].

Text Justification

Given an array of strings words and a width maxWidth, format the text such that each line has exactly maxWidth characters and is fully (left and right) justifie...

Time to Cross a Bridge

There are k workers who want to move n boxes from the right (old) warehouse to the left (new) warehouse. You are given the two integers n and k, and a 2D intege...

Find Largest Value in Each Tree Row

Given the root of a binary tree, return an array of the largest value in each row of the tree (0-indexed).

Maximum Number of Non-overlapping Palindrome Substrings

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

Insert Delete GetRandom O(1) - Duplicates allowed

RandomizedCollection is a data structure that contains a collection of numbers, possibly duplicates (i.e., a multiset). It should support inserting and removing...

Create Binary Tree From Descriptions

You are given a 2D integer array descriptions where descriptions[i] = [parenti, childi, isLefti] indicates that parenti is the parent of childi in a binary tree...

Binary Search Tree Iterator

Implement the BSTIterator class that represents an iterator over the in-order traversal of a binary search tree (BST):

Insert Interval

You are given an array of non-overlapping intervals intervals where intervals[i] = [starti, endi] represent the start and the end of the ith interval and interv...

Minimum Deletions to Make Array Divisible

You are given two positive integer arrays nums and numsDivide. You can delete any number of elements from nums.

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.

Sum of Square Numbers

Given a non-negative integer c, decide whether there're two integers a and b such that a2 + b2 = c.

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...

Valid Triangle Number

Given an integer array nums, return the number of triplets chosen from the array that can make triangles if we take them as side lengths of a triangle.

Rotate List

Given the head of a linked list, rotate the list to the right by k places.

Edit Distance

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

Min Stack

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

Shuffle an Array

Given an integer array nums, design an algorithm to randomly shuffle the array. All permutations of the array should be equally likely as a result of the shuffl...

Word Ladder II

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

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...

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...

Longest Palindromic Substring

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

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...

Fizz Buzz

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

Integer to Roman

Seven different symbols represent Roman numerals with the following values:

Longest Substring Without Repeating Characters

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

House Robber IV

There are several consecutive houses along a street, each of which has some money inside. There is also a robber, who wants to steal money from the homes, but h...

House Robber II

You are a professional robber planning to rob houses along a street. Each house has a certain amount of money stashed. All houses at this place are arranged in...

Diameter of Binary Tree

Given the root of a binary tree, return the length of the diameter of the tree.

Same Tree

Given the roots of two binary trees p and q, write a function to check if they are the same or not.

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.

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.

Minimum Time to Type Word Using Special Typewriter

There is a special typewriter with lowercase English letters 'a' to 'z' arranged in a circle with a pointer. A character can only be typed if the pointer is poi...

Validate Binary Search Tree

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

Next Permutation

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

Reorder List

You are given the head of a singly linked-list. The list can be represented as:

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.