P1337 [JSOI2004]平衡点 / 吊打XXX

Archie

显然这玩意可以胡搞

怎么搞

模拟退火基本知识

#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cmath>
using namespace std;
double delat=0.993;
double ans=1e18,t;
double ansx,ansy;
int n,sx,sy;
struct po{
	int x;
	int y;
	int w;
}p[10005]; 
double caculation(double nx,double ny){
	double re=0;
	for(int i=1;i<=n;++i){
		re+=(double)sqrt((nx-p[i].x)*(nx-p[i].x)+(ny-p[i].y)*(ny-p[i].y))*p[i].w;
	}
	return re;
}
void sa(){
	double x=ansx,y=ansy;
	t=2000;
	while(t>1e-14){
		double nx=x+((rand()<<1)-RAND_MAX)*t;
		double ny=y+((rand()<<1)-RAND_MAX)*t;
//为什么乘t呢，因为温度越高越不稳定啊
		double ansss=caculation(nx,ny);
		double exx=ansss-ans;
		if(exx<0){
			ansx=nx;
			ansy=ny;
			ans=ansss;
			x=nx;
			y=ny; 
		}else if(exp(-exx/t)*RAND_MAX>rand()){
			x=nx;
			y=ny; 
		}
		t*=delat;
	}
} 
int main(){
	srand(20040519);
	srand(rand());
	srand(rand());
	scanf("%d",&n);
	for(int i=1;i<=n;++i){
		scanf("%d%d%d",&p[i].x,&p[i].y,&p[i].w);
		sx+=p[i].x;
		sy+=p[i].y;
	}
	ansx=(double)sx/n;
	ansy=(double)sy/n;
	sa();
	sa();
	sa();
	printf("%.3lf %.3lf",ansx,ansy);
	return 0;
}