LeetCode/Medium

19 Remove Nth Node From End of List

1. Description Given the head of a linked list, remove the nth node from the end of the list and return its head. constraints : The number of nodes in the list is sz. 1

18 4Sum

1. Description Given an array nums of n integers, return an array of all the unique quadruplets [nums[a], nums[b], nums[c], nums[d]] such that : 0

17 Letter Combinations of a Phone Number

1. Description Given a string containing digits from 2-9 inclusive, return all possible letter combinations that the number could represent. Return the answer in any order. A mapping of digits to letters (just like on the telephone buttons) is given below. Not that 1 does not map to any letters. constraints : 0

16 3Sums Closest

1. Description Given an integer array nums of length n and an integer target, find three integers in nums such that the sum is closest to target. Return the sum of the three integers. You may assume that each input would have exactly one solution. constraints : 3