Mapoos

Longest Happy String (M)A string is called happy if it does not have any of the strings 'aaa', 'bbb' or 'ccc' as a substring.Given three integers a, b and c, return any string s, which satisfies fol...

Number of Steps to Reduce a Number in Binary Representation to One (M)Given a number s in their binary representation. Return the number of steps to reduce it to 1 under the following rules:If the ...

Minimum Subsequence in Non-Increasing Order (E)Given the array nums, obtain a subsequence of the array whose sum of elements is strictly greater than the sum of the non included elements in such subs...

Reconstruct Itinerary (M)Given a list of airline tickets represented by pairs of departure and arrival airports [from, to], reconstruct the itinerary in order. All of the tickets belong to a man who ...

Design Underground System (M)Implement the class UndergroundSystem that supports three methods:1.checkIn(int id, string stationName, int t)A customer with id card equal to id, gets in the station ...

Count Number of Teams (M)There are n soldiers standing in a line. Each soldier is assigned a unique rating value.You have to form a team of 3 soldiers amongst them under the following rules:Choose...

Find Lucky Integer in an Array (E)Given an array of integers arr, a lucky integer is an integer which has a frequency in the array equal to its value.Return a lucky integer in the array. If there ar...

Implement strStr() (E)Implement strStr().Return the index of the first occurrence of needle in haystack, or -1 if needle is not part of haystack.Example 1:Input: haystack = "hello", needle = "ll"...

Check if There is a Valid Path in a Grid (M)Given a m x n grid. Each cell of the grid represents a street. The street of grid[i][j] can be:1 which means a street connecting the left cell and the ri...

Longest Happy Prefix (H)A string is called a happy prefix if is a non-empty prefix which is also a suffix (excluding itself).Given a string s. Return the longest happy prefix of s .Return an empty ...

Four Divisors (M)Given an integer array nums, return the sum of divisors of the integers in that array that have exactly four divisors.If there is no such integer in the array, return 0.Example 1:...

Create Target Array in the Given Order (E)Given two arrays of integers nums and index. Your task is to create target array under the following rules:Initially target array is empty.From left to ri...

Maximum Performance of a Team (H)There are n engineers numbered from 1 to n and two arrays: speed and efficiency, where speed[i] and efficiency[i] represent the speed and efficiency for the i-th engi...

Design a Stack With Increment Operation (M)Design a stack which supports the following operations.Implement the CustomStack class:CustomStack(int maxSize) Initializes the object with maxSize which...

Balance a Binary Search Tree (M)Given a binary search tree, return a balanced binary search tree with the same node values.A binary search tree is balanced if and only if the depth of the two subtre...

Lucky Numbers in a Matrix (E)Given a m * n matrix of distinct numbers, return all lucky numbers in the matrix in any order.A lucky number is an element of the matrix such that it is the minimum elem...

Single Number III (M)Given an array of numbers nums, in which exactly two elements appear only once and all the other elements appear exactly twice. Find the two elements that appear only once.Examp...

Bulb Switcher (M)There are n bulbs that are initially off. You first turn on all the bulbs. Then, you turn off every second bulb. On the third round, you toggle every third bulb (turning on if it’s o...

Merge Intervals (M)Given a collection of intervals, merge all overlapping intervals.Example 1:Input: [[1,3],[2,6],[8,10],[15,18]]Output: [[1,6],[8,10],[15,18]]Explanation: Since intervals [1,3] a...

Restore IP Addresses (M)Given a string containing only digits, restore it by returning all possible valid IP address combinations.Example:Input: "25525511135"Output: ["255.255.11.135", "255.255.11...

Frog Position After T Seconds (H)Given an undirected tree consisting of n vertices numbered from 1 to n. A frog starts jumping from the vertex 1. In one second, the frog jumps from its current vertex...

Time Needed to Inform All Employees (M)A company has n employees with a unique ID for each employee from 0 to n - 1. The head of the company has is the one with headID.Each employee has one direct m...

Bulb Switcher III (M)There is a room with n bulbs, numbered from 1 to n, arranged in a row from left to right. Initially, all the bulbs are turned off.At moment k (for k from 0 to n - 1), we turn on...

Generate a String With Characters That Have Odd Counts (E)Given an integer n, return a string with n characters such that each character in such string occurs an odd number of times.The returned str...

Word Break II (H)Given a non-empty string s and a dictionary wordDict containing a list of non-empty words, add spaces in s to construct a sentence where each word is a valid dictionary word. Return ...

LRU Cache (M)Design and implement a data structure for Least Recently Used (LRU) cache. It should support the following operations: get and put.get(key) - Get the value (will always be positive) of ...

Word Break (M)Given a non-empty string s and a dictionary wordDict containing a list of non-empty words, determine if s can be segmented into a space-separated sequence of one or more dictionary word...

Binary Search Tree Iterator (M)Implement an iterator over a binary search tree (BST). Your iterator will be initialized with the root node of a BST.Calling next() will return the next smallest numbe...

Ugly Number II (M)Write a program to find the n-th ugly number.Ugly numbers are positive numbers whose prime factors only include 2, 3, 5.Example:Input: n = 10Output: 12Explanation: 1, 2, 3, 4, ...

Ugly Number (E)Write a program to check whether a given number is an ugly number.Ugly numbers are positive numbers whose prime factors only include 2, 3, 5.Example 1:Input: 6Output: trueExplanat...

Subtree of Another Tree (E)Given two non-empty binary trees s and t, check whether tree t has exactly the same structure and node values with a subtree of s. A subtree of s is a tree consists of a no...

Linked List in Binary Tree (M)Given a binary tree root and a linked list with head as the first node.Return True if all the elements in the linked list starting from the head correspond to some down...

Rank Teams by Votes (M)In a special ranking system, each voter gives a rank from highest to lowest to all teams participated in the competition.The ordering of teams is decided by who received the m...

How Many Numbers Are Smaller Than the Current Number (E)Given the array nums, for each nums[i] find out how many numbers in the array are smaller than it. That is, for each nums[i] you have to count ...

Longest Increasing Subsequence (M)Given an unsorted array of integers, find the length of longest increasing subsequence.Example:Input: [10,9,2,5,3,7,101,18]Output: 4 Explanation: The longest inc...

Largest Multiple of Three (H)Given an integer array of digits, return the largest multiple of three that can be formed by concatenating some of the given digits in any order.Since the answer may not...

Closest Divisors (M)Given an integer num, find the closest two integers in absolute difference whose product equals num + 1 or num + 2.Return the two integers in any order.Example 1:Input: num = 8...

Number of Days Between Two Dates (E)Write a program to count the number of days between two dates.The two dates are given as strings, their format is YYYY-MM-DD as shown in the examples.Example 1:...

Validate Binary Tree Nodes (M)You have n binary tree nodes numbered from 0 to n - 1 where node i has two children leftChild[i] and rightChild[i], return true if and only if all the given nodes form e...

Unique Binary Search Trees II (M)Given an integer n, generate all structurally unique BST’s (binary search trees) that store values 1 … n.Example:Input: 3Output:[ [1,null,3,2], [3,2,null,1],...