60分求助

#include<iostream>
#include<cstdio>
#include<cmath>
using namespace std;
#define NN 20000005
int a[NN];
int n;
void qsort(int left,int right) {
    int i=left,j=right;
    int mid=a[(i+j)/2];
    while(i<=j){
        while(a[i]<mid)i++;
        while(a[j]>mid)j--;
        if(i<=j){
            swap(a[i],a[j]);
            i++;j--;
        }
    }
    if(i<right)qsort(i,right);
    if(j>left)qsort(left,j);
}
int main()
{
    int k;
    scanf("%d%d",&n,&k);
    for(int i=1;i<=n;i++){
        cin>>a[i];
    }
    qsort(1,n);
    cout<<a[k+1];
    return 0;
}