HDU 4355 Party All the Time（三分|二分）

#include<cstdio>  
#include<cstring>  
#include<cmath>  
#include<cstdlib>  
#include<iostream>  
#include<algorithm>  
#include<vector>  
#include<map>  
#include<queue>  
#include<stack> 
#include<string>
#include<map> 
#include<set>
#define eps 1e-6 
#define LL long long  
#define pii pair<int,int>
using namespace std;  

const int maxn = 100000+100;
//const int INF = 0x3f3f3f3f;
double w[maxn], x[maxn];
int n;

double fx(double x0) {
	double ans = 0;
	for(int i = 0; i < n; i++) {
		ans += pow(fabs(x[i]-x0), 3)*w[i];
	}
	return ans;
}

double find(double L, double R) {
	for(int i = 0; i < 30; i++) {
		double midl = L+(R-L)/3, midr = L+(R-L)*2/3;
		if(fx(midl) <= fx(midr)) R = midr;
		else L = midl;
	}
	return R;
}

int main() {
//	freopen("input.txt", "r", stdin);
	int T; cin >> T;
	int kase = 0;
	while(T--) {
		cin >> n;
		double minp = 1000000, maxp = -1000000;
		for(int i = 0; i < n; i++) {
			scanf("%lf%lf", &x[i], &w[i]);
			minp = min(minp, x[i]);
			maxp = max(maxp, x[i]);
		}
//		cout << fx(0) << endl;
		printf("Case #%d: %d\n", ++kase, (int)(fx(find(minp, maxp))+0.5));
	}
	return 0;
}