Algorithms

Question 1

Contains duplicates

Answer 1

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.

Question 2

Two sum

Answer 2

Given an array of numbers [1, 2, 3, 4] and target int 7. Goal is to return indexes of two numbers from the array so the sum of these two would be 7.

Question 3

Valid anagram

Answer 3

Given two strings ‘racecar’, ‘raceacr’. Return if these two words are annagrams.

Question 4

Anagram groups

Answer 4

Given an array of strings (etc [“cat”, “hat,” “atc”]). The goal is to group them. For example in the case above it will be [[“cat”, “atc”], [“hat”]]

Question 5

Top K Frequent Elements

Answer 5

Given an integer array nums and an integer k, return the k most frequent elements within the array. For example: nums = [1,2,2,3,3,3], k = 2 and return [2,3]

Question 6

Validate Parentheses

Answer 6

You are given a string s consisting of the following characters: ‘(‘, ‘)’, ‘{‘, ‘}’, ‘[’ and ‘]’.

Question 7

Min stack

Answer 7

The goal is to build minimal stack functionality with one additional extra feature. This extra feature is returning minimal value in the stack.

Question 8

Valid palindrome

Answer 8

Given a string s, return true if it is a palindrome, otherwise return false.

Question 9

Merge sorted array

Answer 9

You are given two sorted arrays ([1, 2, 3, 0, 0] and [2,5]). The goal is to merge them into one (into the first), sure the new array must be sorted.

Question 10

Remove duplicates from sorted array

Answer 10

You are given two sorted arrays ([1, 2, 3, 0, 0] and [2,5]). The goal is to merge them into one (into the first), sure the new array must be sorted.

Question 11

Move zeroes

Answer 11

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

Note that you must do this in-place without making a copy of the array.

Question 12

Reverse a string

Answer 12

Write a function that reverses a string. The input string is given as an array of characters s.
You must do this by modifying the input array in-place with O(1) extra memory.

Question 13

Squares of sorted array

Answer 13

Given an integer arraynumssorted innon-decreasingorder, returnan array ofthe squares of each numbersorted in non-decreasing order.

Question 14

Two Sum II (input array is sorted)

Answer 14

Given an array of integers numbers that is sorted in non-decreasing order.

Return the indices (1-indexed) of two numbers, [index1, index2], such that they add up to a given target number target and index1 < index2. Note that index1 and index2 cannot be equal, therefore you may not use the same element twice.

Question 15

Invert binary tree

Answer 15

You are given the root of a binary treeroot. Invert the binary tree and return its root.

Question 16

Plus one

Question 17

Maximum Average Subarray I

Answer 17

You are given n integers and some k value. Find k sized subarray that has maximum sum of the elements. Return this value (average)

Input: nums = [1,12,-5,-6,50,3], k = 4
Output: 12.75000

Input: nums = [5], k = 1
Output: 5.00000

Question 18

Minimum Size Subarray Sum

Answer 18

You are given an array of positive integers nums and integer target. Return shortest subarray of nums which sum of elements is greater of equal to target.

Input: target = 7, nums = [2,3,1,2,4,3]
Output: 2

Input: target = 4, nums = [1,4,4]
Output: 1

Question 19

Buy and Sell crypto

Answer 19

Given array of numbers. They represent prices of a stock. Find best time to buy and sell this stock. Return profit.

Question 20

Maximum Subarray

Answer 20

Given an array of integers nums, find the subarray with the largest sum and return the sum.

A subarray is a contiguous non-empty sequence of elements within an array.

Question 21

Maximum Number of Vowels in a substring of given length

Question 22

Linked list cycle