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OI-codes/S2OJ/152/152.cpp

51 lines
973 B
C++

#pragma GCC optimize("Ofast")
#include <bits/stdc++.h>
using namespace std;
long long n, k, a[1000005], sum, cnt, pos, ans, num, res;
bool check(int x);
int main() {
cin >> n >> k;
for (int i = 1; i <= n; i++) {
cin >> a[i];
}
sort(a + 1, a + n + 1);
int l = 1;
int r = a[n] - a[1];
while (l <= r) {
int mid = l + r >> 1;
if (check(mid)) {
r = mid - 1;
num = cnt;
pos = mid;
ans = res;
} else {
l = mid + 1;
}
}
cout << ans - (num - k) * pos << endl;
return 0;
}
bool check(int x) {
cnt = 0;
res = 0;
sum = 0;
queue<int> q;
for (int i = 1; i <= n; i++) {
while (!q.empty() && a[i] - a[q.front()] > x) {
sum -= a[q.front()];
q.pop();
}
cnt += q.size();
res += q.size() * a[i] - sum;
q.push(i);
sum += a[i];
}
return cnt >= k;
}