Leetcode

Problem You are given an array happiness of length n, and a positive integer k. There are n children standing in a queue, where the ith child has happiness value happiness[i]. You want to select k children from these n children in k turns. In each turn, when you select a child, the happiness value of all the children that have not been selected till now decreases by 1. Note that the happiness value cannot become negative and gets decremented only if it is positive. ...

Problem You are given an integer array score of size n, where score[i] is the score of the ith athlete in a competition. All the scores are guaranteed to be unique. The athletes are placed based on their scores, where the 1st place athlete has the highest score, the 2nd place athlete has the 2nd highest score, and so on. The placement of each athlete determines their rank: ...

Double a Number Represented as a Linked List Problem You are given the head of a non-empty linked list representing a non-negative integer without leading zeroes. Return the head of the linked list after doubling it. Examples Example 1: --- title: Input --- graph LR; 1 --> 8 --> 9 --- title: Output --- graph LR; 3 --> 7 --> 8 ...

Problem Given an integer array nums that does not contain any zeros, find the largest positive integer k such that -k also exists in the array. Return the positive integer k. If there is no such integer, return -1. Examples Example 1: Input: nums = [-1,2,-3,3] Output: 3 Explanation: 3 is the only valid k we can find in the array. ...

2Sum Problem Problem Given a 0-indexed string word and a character ch, reverse the segment of word that starts at index 0 and ends at the index of the first occurrence of ch (inclusive). If the character ch does not exist in word, do nothing. For example, if word = "abcdefd" and ch = "d", then you should reverse the segment that starts at 0 and ends at 3 (inclusive). The resulting string will be "dcbaefd". Return the resulting string. ...

Problem Given a collection of numbers, nums, that might contain duplicates, return all possible unique permutations in any order. Example 1: Input: nums = [1,1,2] Output: [ [1,1,2], [1,2,1], [2,1,1] ] ...

Problem Given an array of distinct integers nums and a target integer target, return the number of possible combinations that add up to target. The test cases are generated so that the answer can fit in a 32-bit integer. Examples Example 1: Input: nums = [1,2,3], target = 4 Output: 7 Explanation: The possible combination ways are: (1, 1, 1, 1) (1, 1, 2) (1, 2, 1) (1, 3) (2, 1, 1) (2, 2) (3, 1) Note that different sequences are counted as different combinations. ...

Problem Given an integer array nums and an integer k, return true if nums has a continuous subarray of size at least two whose elements sum up to a multiple of k, or false otherwise. An integer x is a multiple of k if there exists an integer n such that x = n * k. 0 is always a multiple of k. Examples Example 1: ...

Problem Given an array nums containing n distinct numbers in the range [0, n], return the only number in the range that is missing from the array. Examples Example 1: Input: nums = [3,0,1] Output: 2 Explanation: n = 3 since there are 3 numbers, so all numbers are in the range [0,3]. 2 is the missing number in the range since it does not appear in nums. ...

Problem 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 [-2^31, 2^31 - 1], then return 0. Assume the environment does not allow you to store 64-bit integers (signed or unsigned). Examples Example1: x = 123, return 321 Example2: x = -123, return -321 ...