Given an array and a value, remove all instances of that value in-place and return the new length. Do not allocate extra space for another array, you must do this by modifying the input array in-place with O(1) extra memory. The order of elements can be changed. It doesn't matter what you leave beyond the new length. Example: Given nums = [3,2,2,3], val = 3, Your function should return length = 2, with the first two elements of nums being 2.