快速排序方法：

#include <bits/stdc++.h>
using namespace std;
struct P 
   { 
	   int k, s;
   } a[5005];

void qksrt(P a[], int l, int r) {
	if (l >= r) return;
	int i = l, j = r;
	P pvt = a[(l + r) / 2];
	while (i <= j) {
		while (a[i].s > pvt.s || (a[i].s == pvt.s && a[i].k < pvt.k)) i++;
		while (a[j].s < pvt.s || (a[j].s == pvt.s && a[j].k > pvt.k)) j--;
		if (i <= j) {
			swap(a[i], a[j]);
			i++; j--;
		}
	}
	qksrt(a, l, j);
	qksrt(a, i, r);
}

int main() {
	int n, m; cin >> n >> m;
	for (int i = 0; i < n; i++) cin >> a[i].k >> a[i].s;
	qksrt(a, 0, n-1);
	int x = m * 3 / 2;
	int ln = a[x-1].s;
	int cnt = 0;
	while (cnt < n && a[cnt].s >= ln) cnt++;
	cout << ln << ' ' << cnt << '\n';
	for (int i = 0; i < cnt; i++)
		cout << a[i].k << ' ' << a[i].s << '\n';
	return 0;
}

原题解：

//方法1： sort排序
#include <bits/stdc++.h>
using namespace std;

struct Student{
    int name;
    int score;
};

bool cmp(Student a,Student b){
    if(a.score==b.score){
        return a.name<b.name;
    }else{
        return a.score>b.score;
    }
}
int main(){
    int n, m, i, a, b, x, y=0;
    cin >> n >> m;
    struct Student t[10000];
    for (i = 0; i < n; i++){
        cin >> t[i].name >> t[i].score;
    }
    sort(t, t + n, cmp);
    x = floor(m * 3 / 2);
    for (i = 0; i < n; i++) {
        if (t[i].score>= t[x - 1].score) {
            y++;
        }
    }
    cout << t[x - 1].score << " " << y << endl;
    for (int i = 0; i < y; i++){
        cout << t[i].name << " " << t[i].score;
        cout<<endl;
    }
    return 0;
}