[Round 1C 2017] Problem A. Ample Syrup : https://code.google.com/codejam/contest/3274486/dashboard#s=p0&a=0

Ample Syrup.cpp

//
//  Created by fpdjsns
//  Copyright © 2019 fpdjsns. All rights reserved.
//
#include<iostream>
#include<vector>
#include<algorithm>
#include<string>
#include<queue>

using namespace std;

int main() {
	int T;
	cin >> T;

	double PI = 3.1415926535897932;

	for (int c = 1; c <= T; c++) {

		int N, K;
		cin >> N >> K;
		vector<pair<int, int>> arr(N);//R, H 
		for (int i = 0; i < N; i++){
			cin >> arr[i].first >> arr[i].second;
		}
		sort(arr.begin(), arr.end());
		long long int answer = 0;
		long long int R = 0;
		long long int H = 0;
		long long int sumH = 0;
		priority_queue<long long int,vector<long long int>,greater<long long int>> q;
		for (int i = 0; i < K; i++) {
			R = arr[i].first;
			H = 2*R*arr[i].second;
			q.push(H);
			sumH += H;
		}
		answer = R * R + sumH;
		for (int biggest = K; biggest < N; biggest++) {
			R = arr[biggest].first;
			H = 2*R*arr[biggest].second;
			sumH += H;
			sumH -= q.top();
			q.pop();
			q.push(H);
			answer = max(answer, R*R + sumH);
		}

		/* output */
		printf("Case #%d: %7lf\n", c, answer * PI);
	}
	return 0;
}