Leetcode

Count Primes Problem Given an integer n, return the number of prime numbers that are strictly less than n. Examples Example 1: Input: n = 10 Output: 4 Explanation: There are 4 prime numbers less than 10, they are 2, 3, 5, 7. ...

Problem Given a string expression of numbers and operators, return all possible results from computing all the different possible ways to group numbers and operators. You may return the answer in any order. Examples Example 1: Input: expression = "2-1-1" Output: [0,2] Explanation: ((2-1)-1) = 0 (2-(1-1)) = 2 ...

Problem Numbers can be regarded as product of its factors. For example, 8 = 2 x 2 x 2; = 2 x 4. Write a function that takes an integer n and return all possible combinations of its factors. Note: You may assume that n is always positive. Factors should be greater than 1 and less than n. Examples Example 1: ...

Problem Given that integers are read from a data stream. Find median of elements read so for in efficient way. OR Numbers are randomly generated and passed to a method. Write a program to find and maintain the median value as new values are generated. OR You are given a stream of numbers which can be positive or negative. You are required to provide an operation FIND MEDIAN..which when invoked should be able return the median of the numbers in stream(in say O(1) time) ...

Problem Given a string n representing an integer, return the closest integer (not including itself), which is a palindrome. If there is a tie, return the smaller one. The closest is defined as the absolute difference minimized between two integers. Examples Example 1: Input: n = "123" Output: "121" Example 2: Input: n = "1" Output: "0" Explanation: 0 and 2 are the closest palindromes but we return the smallest which is 0. ...

Problem The chess knight has a unique movement, it may move two squares vertically and one square horizontally, or two squares horizontally and one square vertically (with both forming the shape of an L). The possible movements of chess knight are shown in this diagaram: A chess knight can move as indicated in the chess diagram below: ...

Problem 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 histogram. Examples Example 1: Input: heights = [2,1,5,6,2,3] Output: 10 Explanation: The above is a histogram where width of each bar is 1. The largest rectangle is shown in the red area, which has an area = 10 units. ...

Problem Given an integer n, return the least number of perfect square numbers that sum to n. A perfect square is an integer that is the square of an integer; in other words, it is the product of some integer with itself. For example, 1, 4, 9, and 16 are perfect squares while 3 and 11 are not. Examples Example 1: Input: n = 12 Output: 3 Explanation: 12 = 4 + 4 + 4. ...

Problem 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 downward path connected in the binary tree otherwise return False. In this context downward path means a path that starts at some node and goes downwards. Examples Example 1: ...

Problem Given a string s which consists of lowercase or uppercase letters, return the length of the longest palindrome that can be built with those letters. Letters are case sensitive, for example, "Aa" is not considered a palindrome here. Examples Example 1: Input: s = "abccccdd" Output: 7 Explanation: One longest palindrome that can be built is "dccaccd", whose length is 7. ...