阅读程序【CSP 2023 提高级第一轮3】
#include <vector>
#include <algorithm>
#include <iostream>
using namespace std;
bool f0(vector<int> &a, int m, int k) {
int s = 0;
for (int i = 0, j = 0; i < a.size(); i++) {
while (a[i] - a[j] > m)
j++;
s += i - j;
}
return s >= k;
}
int f(vector<int> &a, int k) {
sort(a.begin(), a.end());
int g = 0;
int h = a.back() - a[0];
while (g < h) {
int m = g + (h - g) / 2;
if (f0(a, m, k)) {
h = m;
}
else {
g = m + 1;
}
}
return g;
}
int main() {
int n, k;
cin >> n >> k;
vector<int> a(n, 0);
for (int i = 0; i < n; i++) {
cin >> a[i];
}
cout << f(a, k) << endl;
return 0;
}假设输入总是合法的且 $1 \le a_i \le 10^8, n le 10000, 1 \le k \le \dfrac {n(n-1)} 2$，完成下面的判断题和单选题:
