LeetCode——Sort Colors

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?

原题链接：https://oj.leetcode.com/problems/sort-colors/

题目：给定一个数组，有n个对象，其中有红色，白色，蓝色，将他们排序，使得相同的颜色相邻，结果为红 白 蓝这样的顺序。

这里分别用0 1 2 代表红 白 蓝。

	public void sortColors(int[] A) {
		int len = A.length;
		int index = -1;
		for (int i = 0; i < len; i++) {
			if (A[i] == 0) {
				index++;
				swap(A, i, index);
			}
			if (A[i] == 2) {
				len--;
				swap(A, i, len);
				i--;
			}
		}
	}

	private void swap(int[] A, int i, int j) {
		int tmp = A[i];
		A[i] = A[j];
		A[j] = tmp;
	}