//Given a string s containing just the characters '(', ')', '{', '}', '[' and '] //', determine if the input string is v

//Given the head of a linked list, remove the nth node from the end of the list //and return its head. // // // Examp

//Given a string containing digits from 2-9 inclusive, return all possible lette //r combinations that the number could

//Given an integer array nums, return all the triplets [nums[i], nums[j], nums[k //]] such that i != j, i != k, and j !=