27. Remove Element

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 in place with constant memory.

The order of elements can be changed. It doesn't matter what you leave beyond the new length.

Example:
Given input array nums = [3,2,2,3], val = 3

Your function should return length = 2, with the first two elements of nums being 2.

Solution:

Tips:

if find target value in array from left to right, then find a non-target value from right to left, then swap them.

Java Code:

public class Solution {    public int removeElement(int[] nums, int val) {        if (null == nums) { // null check            return 0;        }                int left = 0;        int right = nums.length;                while (left < right) {            if (nums[left] == val) {                if (nums[right - 1] == val) {                    right--;                } else {                    nums[left] = nums[right - 1];                    left++;                    right--;                }            } else {                left++;            }        }                return left;    }}