Sort Colors <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.

思路：该题很简单，直接把快排实现以下，代码如下：

class Solution {
public:
    void sortColors(int A[], int n) {
        if(n==1)  return;
        quick_sort(A,0,n-1);
    }
    
    void quick_sort(int A[],int l,int r)
    {
        if(l>=r)  return;
        else
        {
           int mid=fen(A,l,r);
           quick_sort(A,l,mid-1);
           quick_sort(A,mid+1,r);
        }
    }
    
    int fen(int A[],int  l,int r)
    {
        int k=A[l];
        int i=l;
        int j=r;
        while(i<j)
        {
            while(A[i]<=k&&i<j){i++;}
            while(A[j]>=k&&i<j){j--;}
           
            swap(A[i],A[j]);
        }
        if(A[l]>A[i])
        {
          swap(A[l],A[i]);
          return i;
        }
        else
        {
        swap(A[l],A[i-1]);
           return i-1;
        }
    }
};