AC了

#include<bits/stdc++.h>
using namespace std;
 
inline int read(){
	int f=1,x=0; char s=getchar();
	while(s<'0' || s>'9') {if(s=='-')f=-1;s=getchar();}
	while(s>='0' && s<='9') {x = x*10+s-'0';s=getchar();}
	return x*f;
}
 
struct node{
	int x,y;
	void Read()
	{
		x = read(); y = read();
	}
}a[20010];
int n; 
 
bool cmp(node a,node b)
{
	if (a.x == b.x) return a.y<b.y; else return a.x<b.x;
}
 
int main()
{
	scanf("%d",&n);
	long long sumx = 0 , sumy = 0;
	for (int i = 1 ; i <= n ; i++) {
		a[i].Read();
		sumx += a[i].x; sumy += a[i].y;
	}
	double xx = sumx*1.0/n , yy = sumy*1.0/n;
	int tx = floor(xx*2) , ty = floor(yy*2);
	bool f = 1;
	sort(a+1,a+1+n,cmp);
	for (int i = 1 ; i <= n/2; i ++)
		if (a[i].x+a[n-i+1].x != tx || a[i].y+a[n-i+1].y != ty) 
		{
			f = 0;
			break;
		}
	if (f == 1) printf("V.I.P. should stay at (%.1f,%.1f).\n",xx,yy);
	else printf("This is a dangerous situation!");
	return 0;
}
解释