820复试算法 快排找第 k 小

done {20-01-30 12:56}

ref:

https://blog.csdn.net/fengsigaoju/article/details/50728588

note:

void quicksort(int a[],int left,int right,int k)
{
    int i,j,key,low,high;
    low=left;
    high=right;
    key=a[left];
    if (left<right)
    {
        while(low<high)
        {
        	//hplc ; high pass, low change
            while((low<high)&&(a[high]>=key)){
                high--;
                a[low]=a[high];
            }
            //lphc: low pass, high change
            while((low<high)&&(a[low]<=key)){
                low++;
            	a[high]=a[low];
            }
        }
        a[low]=key;
        //now 左右都归位：左边都小，右边都大的
        if (low==k-1)
            printf("%d\n",a[low]);
        else
        {
            if (low<k-1)
                quicksort(a,low+1,right,k);
            else
                quicksort(a,left,low-1,k);
        }
    }
}

todo {20-01-29 12:56}