283. Move Zeroes

Given an array nums, write a function to move all 0's to the end of it while maintaining the relative order of the non-zero elements.

For example, given nums = [0, 1, 0, 3, 12], after calling your function, nums should be [1, 3, 12, 0, 0].

Note:

1. You must do this in-place without making a copy of the array.
2. Minimize the total number of operations.

move zero的题，要用2个pointer，一个i遍历数组，表示当前数组的每一项，另一个j表示不为0的下一个数的下标，即第一个为0的数的下标，当nums[i]不为0时，把它和nums[j]互换，更新j的值

代码如下：

class Solution {
public:
    void moveZeroes(vector<int>& nums) {
        int j = 0;
        for (int i = 0; i < nums.size(); i++) {
            if (nums[i] != 0) {
                if (i != j) {
                    nums[j] = nums[i];
                    nums[i] = 0;
                }
                j++;
            }
        }
        return ;
    }
};