Sort Colors

Given an array with n objects colored red, white or blue, sort them so that objects of the same color are adjacent, with the colors in the order red, white and blue.

Here, we will use the integers 0, 1, and 2 to represent the color red, white, and blue respectively.

Note:
You are not suppose to use the library's sort function for this problem.

有点类似于快排。

class Solution {
public:
    void sortColors(int A[], int n) {
        int pos= sort(A,n-1,2);
        sort(A,pos-1,1);
    }
    int sort(int A[], int end,int target){
        int i=0;
        int j=end;
        for(;;){
            while(i<=end&&A[i]!=target){i++;}
            while(j>=0&&A[j]==target){j--;}
            if(i<j){
                swap(A[i],A[j]);
            }else
                break;
        }
        //i可能越界
        return i;
    }
};