[算法] 快速排序

参考 http://www.cnblogs.com/morewindows/archive/2011/08/13/2137415.html

     http://baike.baidu.com/view/19016.htm?fromId=115472

 #define MAXLENGTH 10

void quick_sort(int a[], int start, int end)
{
    if(start<end){
    int key=a[start];//开始比较对象
    int i=start;       
    int j=end;
    while (i<j) {
        while (i<j &&a[j]>=key) {
            j--;             //开始比较右边，直到发现小于key的数
        }
        if(i<j){
             a[i]=a[j];    
            a[j]=key;    //交换
             i++;
        }
        while (i<j && a[i]<key) {
            i++;
        }
        if(i<j){
           a[j]=a[i];
            a[i]=key;
             j--;
        }
    }
      a[i]=key;
   
        quick_sort(a,start,i-1);//左边
         quick_sort(a, i+1, end);//右边
    }

}

int main(int argc, const char * argv[])
{

    
    @autoreleasepool {
      
        int a[MAXLENGTH]={9,56,45,76,23,45,37,12,19,3};
        for (int b=0; b<MAXLENGTH ; b++) {
            printf("%3d",a[b]);

                    }
        quick_sort(a,0,MAXLENGTH-1);//起始位置,结束位置

         printf("\n");
        for (int b=0; b<MAXLENGTH; b++) {
            printf("%3d",a[b]);
   
        }
        
    }
    return 0;
}