Remove Element

Problem:

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.

Analysis:
Standard two pointer problem.

Solution:

class Solution {
    public int removeElement(int[] nums, int val) {
        if (nums == null) return 0;
        int  i = 0; 
        for (int j = 0; j < nums.length; j++) {
            if (nums[j] != val) {
                nums[i++] = nums[j];
            }
        }
        return i;
    }
}