Implement next permutation, which rearranges numbers into the lexicographically next greater permutation of numbers.

Given an array and a value, remove all instances of that value in place and return the new length.

Given a sorted array, remove the duplicates in place such that each element appear only once and return the new length.

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

Write a function to find the longest common prefix string amongst an array of strings.