283. Move Zeroes

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.

Thoughts

Again, use two indicators, one is the index in loop, the other represents zero number. Then swap the values when meet the non-zero number (because we want to move all 0's to the end), and update the zero-idx.

   ↓ for-loop-idx
+------------------------------+
|  0  |  1  |  0  |  3  |  12  |
+------------------------------+
   ^ z-idx

Solution

public class Solution {
    public void moveZeroes(int[] nums) {
        // j: zero-index
        for (int i = 0, j = 0; i < nums.length && j < nums.length; i++) {
            if (nums[i] != 0) {    // swap
                int temp = nums[i];
                nums[i] = nums[j];
                nums[j] = temp;
                j++;    // update the zero-idx
            }
        }
    }
}