[leetcode]Sort Colors

荷兰三色旗问题。学以致用，理解更深刻了。顺便参看一下非常精简的一个解法，其实本质一样：http://discuss.leetcode.com/questions/251/sort-colors

public class Solution {
    public void sortColors(int[] A) {
        // Start typing your Java solution below
        // DO NOT write main() function
        int len = A.length;
        if (len == 0) return;
        
        int i = 0;
        while (i < len && A[i] == 0) i++;
        
        int j = len - 1;
        while (j >= 0 && A[j] == 2) j--;
        
        for (int k = i; k <= j;) {
            if (A[k] == 0) {
        		int tmp = A[i];
        		A[i] = A[k];
        		A[k] = tmp;
        		
        		i++;
        		if (k < i) k = i;
        	}
        	else if (A[k] == 2) {
        		int tmp = A[j];
        		A[j] = A[k];
        		A[k] = tmp;
        		j--;
        	}
        	else {k++;}
        }
    }
}