BOJ 22986 - Flat Earth [C++]

문제

링크

풀이

#include <algorithm>
#include <iostream>
using namespace std;
 
inline long long calc(long long x) {
  return x * (x + 1) * 2;
}
 
void solve(void) {
  long long n, k; cin >> n >> k;
 
  cout << calc(n) - calc(max(0LL, n-k-1)) << "\n";
}
 
int main(void) {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
 
  int t; cin >> t;
  while (t--) solve();
  return 0;
}