Sort Colors_sorting colored array

Follow up:
A rather straight forward solution is a two-pass algorithm using counting sort.
First, iterate the array counting number of 0's, 1's, and 2's, then overwrite array with total number of 0's, then 1's and followed by 2's.

Could you come up with an one-pass algorithm using only constant space?

Analyze:

We use two pointers to point to the places where 0 and 2 should be inserted. We use another pointer to enumerate all the values in the array.

Code:

public class Solution {
    public void sortColors(int[] A) {
        if (A == null || A.length == 0) return;
        int left = 0;
        int right = A.length - 1;
        int cur = left;
        
        while(cur <= right) {
        	if (A[cur] == 0) {
        		swap(A, left++, cur);
        		cur = (cur <= left) ? left : cur;
        	} else if (A[cur] == 2) {
        		swap(A, right--, cur);
        	} else {
        		cur++;
        	}
        }
    }
    public void swap(int[] A, int i, int j) {
        int temp = A[i];
        A[i] = A[j];
        A[j] = temp;
    }
}