leetcode--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.

双指针交换。

java：

public class Solution {
    public void sortColors(int[] A) {
        int len=A.length;
        int pos = sort(A,len-1,2);
        sort(A,pos-1,1);
    }
    public int sort(int[] A, int end, int target){
        int i=0,j=end;
        while(i<=j){
            if(A[i]==target){
                if(A[j]!=target){
                    swap(A,i,j);
                    j--;
                }else{
                    j--;
                }
            }else{
                i++;
            }
        }
        return i;
    }
    public void swap(int[] A, int i, int j){
        int tmp = A[i];
        A[i]=A[j];
        A[j]=tmp;
    }
}

c++：

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,j=end;
        while(i<=j){
            if(A[i]==target){
                if(A[j]!=target){
                    swap(A[i],A[j]);
                    j--;
                }else{
                    j--;
                }
            }else{
                i++;
            }
        }
        return i;
    }
};