无语，快排怎么还是TLE了

#include<bits/stdc++.h>
using namespace std;
int part(int* r,int left,int right)
{
	int i=left,j=right,pivot=r[left];
	while(i<j){
		while(i<j&&r[j]>pivot){
			j--;
		}
		
		if(i<j){
			swap(r[i++],r[j]);
		}
		
		while(i<j&&r[i]<=pivot){
			i++;
		}
		
		if(i<j)
		{
			swap(r[i],r[j--]);
		}
	}
	return i;
	
}
void Quicksort(int* r,int left,int right){
	int mid;
	if(left<right){
		mid = part(r,left,right);
		Quicksort(r,left,mid-1);
		Quicksort(r,mid+1,right);
	}
}
int main(){
	int n,k;
	cin>>n;
	cin>>k;
	int a[n];
	for(int i=0;i<n;i++){
		cin>>a[i];
	}
	Quicksort(a,0,n-1);
	cout<<a[k]<<endl;
	return 0;
}