快读+快写+sort能过（亲测）

#include<bits/stdc++.h>
using namespace std;
int read(){
	int x=0,f=1;
	char c=getchar();
	while(c<'0'||c>'9'){
		if(c=='-'){
			f=-1;
		}
		c=getchar();
	}
	while(c>='0'&&c<='9'){
		x=x*10+c-'0';
		c=getchar();
	}
	return x*f;
}
void write(int x){
	if(x<0){
		x=-x;
		putchar('-');
	}
	if(x>9){
		write(x/10);
	}
	putchar(x%10+'0');
}
int x[5000005],k,n;
int main(){
	n=read();k=read();
	for(int i=0;i<n;i++){
	    x[i]=read();
	}
	sort(x,x+n);
	write(x[k]);
	return 0;
}

8ms/836.00KB AC #1 Accepted, 得分 20.ok accepted 7ms/828.00KB
AC #2 Accepted, 得分 20.ok accepted 9ms/724.00KB
AC #3 Accepted, 得分 20.ok accepted 421ms/18.42MB
AC #4 Accepted, 得分 20.ok accepted 495ms/19.46MB
AC #5 Accepted, 得分 20.ok accepted