洛谷 P1227 [JSOI2008]完美的对称

传送门

题目大意：求一些点集的公共对称中心

#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cstring>
#define N 20009
using namespace std;

int n;

struct W{
double x,y;
}w
;

bool cmp(W a,W b){
if(a.x==b.x)return a.y<b.y;
return a.x<b.x;
}

int main(){
scanf("%d",&n);
for(int i=1;i<=n;i++){
scanf("%lf%lf",&w[i].x,&w[i].y);
}
sort(w+1,w+n+1,cmp);
double xx=(w[1].x+w
.x)/2.0;
double yy=(w[1].y+w
.y)/2.0;
for(int i=2;i<=n;i++){
if(n-i+1<=i)break;
double tx=(w[i].x+w[n-i+1].x)/2.0;
double ty=(w[i].y+w[n-i+1].y)/2.0;
if(tx!=xx||ty!=yy){
printf("This is a dangerous situation!\n");
return 0;
}
}
printf("V.I.P. should stay at (%.1lf,%.1lf).",xx,yy);
return 0;
}