Yandex Coding Interview Questions

Longest Subarray of 1's After Deleting One Element

Given a binary array nums, you should delete one element from it.

Summary Ranges

You are given a sorted unique integer array nums.

String Compression

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

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.

Isomorphic Strings

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

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.

Permutation in String

Given two strings s1 and s2, return true if s2 contains a permutation of s1, or false otherwise.

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...

Insert Delete GetRandom O(1)

Implement the RandomizedSet class:

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.

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...

Group Anagrams

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

Two Sum

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

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.

Valid Parentheses

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

Valid Palindrome II

Given a string s, return true if the s can be palindrome after deleting at most one character from it.

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...

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.

Find All Anagrams in a String

Given two strings s and p, return an array of all the start indices of p's anagrams in s. You may return the answer in any order.

Min Stack

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

Longest Palindromic Substring

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

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...

Design an ATM Machine

There is an ATM machine that stores banknotes of 5 denominations: 20, 50, 100, 200, and 500 dollars. Initially the ATM is empty. The user can use the machine to...

Generate Parentheses

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

LRU Cache

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

Is Subsequence

Given two strings s and t, return true if s is a subsequence of t, or false otherwise.

Evaluate Reverse Polish Notation

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

Merge Two Sorted Lists

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

Validate Binary Search Tree

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

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...

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.

Destination City

You are given the array paths, where paths[i] = [cityAi, cityBi] means there exists a direct path going from cityAi to cityBi. Return the destination city, that...

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.

Lowest Common Ancestor of a Binary Tree

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

Find Duplicate Subtrees

Given the root of a binary tree, return all duplicate subtrees.

Merge k Sorted Lists

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

Simplify Path

You are given an absolute path for a Unix-style file system, which always begins with a slash '/'. Your task is to transform this absolute path into its simplif...

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.

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...

Intersection of Two Arrays II

Given two integer arrays nums1 and nums2, return an array of their intersection. Each element in the result must appear as many times as it shows in both arrays...

Symmetric Tree

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

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).

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...

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]).

Single Number

Given a non-empty array of integers nums, every element appears twice except for one. Find that single one.

Remove Element

Given an integer array nums and an integer val, remove all occurrences of val in nums in-place. The order of the elements may be changed. Then return the number...

Max Consecutive Ones

Given a binary array nums, return the maximum number of consecutive 1's in the array.

Add Two Numbers

You are given two non-empty linked lists representing two non-negative integers. The digits are stored in reverse order, and each of their nodes contains a sing...

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].

Candy

There are n children standing in a line. Each child is assigned a rating value given in the integer array ratings.

Continuous Subarray Sum

Given an integer array nums and an integer k, return true if nums has a good subarray or false otherwise.

Longest Increasing Subsequence

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

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...

Longest Substring with At Least K Repeating Characters

Given a string s and an integer k, return the length of the longest substring of s such that the frequency of each character in this substring is greater than o...

Longest Repeating Character Replacement

You are given a string s and an integer k. You can choose any character of the string and change it to any other uppercase English character. You can perform th...

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.

Valid Anagram

Given two strings s and t, return true if t is an anagram of s, and false otherwise.

Perfect Squares

Given an integer n, return the least number of perfect square numbers that sum to n.

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:

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...

Two Sum II - Input Array Is Sorted

Given a 1-indexed array of integers numbers that is already sorted in non-decreasing order, find two numbers such that they add up to a specific target number....

Reverse Integer

Given a signed 32-bit integer x, return x with its digits reversed. If reversing x causes the value to go outside the signed 32-bit integer range [-231, 231 - 1...

Best Time to Buy and Sell Stock II

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

Palindrome Number

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

Kth Largest Element in an Array

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

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.

Balanced Binary Tree

Given a binary tree, determine if it is height-balanced.

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.

Contains Duplicate

Given an integer array nums, return true if any value appears at least twice in the array, and return false if every element is distinct.

Remove Duplicates from Sorted Array II

Given an integer array nums sorted in non-decreasing order, remove some duplicates in-place such that each unique element appears at most twice. The relative or...

Reverse Linked List

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

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.

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...

Top K Frequent Words

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

Reverse Words in a String III

Given a string s, reverse the order of characters in each word within a sentence while still preserving whitespace and initial word order.

Sort the Matrix Diagonally

A matrix diagonal is a diagonal line of cells starting from some cell in either the topmost row or leftmost column and going in the bottom-right direction until...

Palindrome Linked List

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

Majority Element

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

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...

Maximum Depth of Binary Tree

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

Longest Consecutive Sequence

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

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.

Contains Duplicate III

You are given an integer array nums and two integers indexDiff and valueDiff.

Palindrome Pairs

You are given a 0-indexed array of unique strings words.

Climbing Stairs

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

Find the Difference of Two Arrays

Given two 0-indexed integer arrays nums1 and nums2, return a list answer of size 2 where:

Robot Return to Origin

There is a robot starting at the position (0, 0), the origin, on a 2D plane. Given a sequence of its moves, judge if this robot ends up at (0, 0) after it compl...

Path Crossing

Given a string path, where path[i] = 'N', 'S', 'E' or 'W', each representing moving one unit north, south, east, or west, respectively. You start at the origin...

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.

Search a 2D Matrix

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

Rotate Image

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

Non-overlapping Intervals

Given an array of intervals intervals where intervals[i] = [starti, endi], return the minimum number of intervals you need to remove to make the rest of the int...