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.

解题思路

用两个指针i，j分别指向0和非零，当j指向非零时，交换两个指针所指向的元素，并且i向前走一步；j则每次循环无论是否交换都向前走一步。

实现代码

C++：

// Runtime: 20 ms
class Solution {
public:
    void moveZeroes(vector<int>& nums) {
        int i = 0;
        int j = 0;
        while (j < nums.size())
        {
            if (nums[j] != 0)
            {
                swap(nums[i], nums[j]);
                i++;
            }
            j++;
        }
    }
};

Java：

// Runtime: 1 ms
public class Solution {
    public void moveZeroes(int[] nums) {
        int i = 0;
        int j = 0;
        while (j < nums.length) {
            if (nums[j] != 0) {
                if (j != i) {
                    int temp = nums[i];
                    nums[i] = nums[j];
                    nums[j] = temp;
                }
                i++;
            }
            j++;
        }
    }
}