微软2014编程之美初赛第一场——题目3 : 活动中心

输入的一组点中找出左右边界，作为起始边界。
while(右边界-左边界<精度){
将左右边界构成的线段均匀分成3段，判断分割点的距离关系，抹去距离大的一段。更新左右边界。
}
输出左(右)边界

#include <iostream>
#include <vector>
#include <cmath>
#include <iomanip>
using namespace std;

struct Point
{
int x;
int y;
};

double calc(double x, vector<Point> points)
{
double distance = 0;
for (int i = 0; i < points.size(); ++i){
double d = (points[i].x - x)*(points[i].x - x) + (points[i].y)*(points[i].y);
distance += sqrt(d);
}

return distance;
}

int main()
{
int T;
cin >> T;
for(int casenum = 0; casenum < T; ++casenum){
int N;
cin >> N;
vector<Point> points;
Point p;
double maxX = -1000000;
double minX = 1000000;
for (int i = 0; i < N; ++i){
cin >> p.x >> p.y;
if (p.x < minX){
minX = p.x;
}
if (p.x > maxX){
maxX = p.x;
}
points.push_back(p);
}
double left = minX;
double right = maxX;
double m1, m2;

while (right - left >= 5e-8){
m1 = (left * 2 + right) / 3.0;
m2 = (right * 2 + left) / 3.0;
double v1 = calc(m1, points);
double v2 = calc(m2, points);
if (v1 < v2){
right = m2;
}
else{
left = m1;
}
}

cout << fixed << setprecision(8);
cout << "Case " << casenum+1 << ": " << left << endl;
}

//system("pause");

return 0;
}