283 Move Zeroes

283. Move Zeroes

1. Question

Given an arraynums, write a function to move all0's to the end of it while maintaining the relative order of the non-zero elements.

For example, givennums = [0, 1, 0, 3, 12], after calling your function,numsshould 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.

2. Implementation

(1) Two Pointers

class Solution {
    public void moveZeroes(int[] nums) {
        if (nums == null || nums.length == 0) {
            return;
        }

        int nonZeroIndex = 0;

        for (int i = 0; i < nums.length; i++) {
            if (nums[i] != 0) {
                swap(nums, nonZeroIndex, i);
                ++nonZeroIndex;
            }
        }
    }

    public void swap(int[] nums, int index1, int index2) {
        if (index1 == index2) {
            return;
        }

        int temp = nums[index1];
        nums[index1] = nums[index2];
        nums[index2] = temp;
    }
}

3. Time & Space Complexity

Two Pointers: 时间复杂度O(n), 空间复杂度O(1)