source：P9064
排序，然后对连续m个计算一下更新一下答案即可
#include <bits/stdc++.h>
using namespace std;
int a[100005];
int main() {
int n, m, ans = 1e9;
cin >> n >> m;
for (int i = 1; i <= n; i++) cin >> a[i];
sort(a + 1, a + n + 1);
for (int i = 1; i <= n - m + 1; i++) {
ans = min(ans, a[i + m - 1] - a[i]);
}
cout << ans;
}