LG1337 [JSOI2004]平衡点 / 吊打XXX 模拟退火

问题描述

LG1337

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题解

模拟退火模板

记住概率公式： (exp(frac{dealt}{T}) imes rand ge R_A^ND^M_AX)

zzk太欧了，我交了一版没过他来了一下就A了。

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(mathrm{Code})

#include<bits/stdc++.h>
using namespace std;

template <typename Tp>
void read(Tp &x){
	x=0;char ch=1;int fh;
	while(ch!='-'&&(ch>'9'||ch<'0')) ch=getchar();
	if(ch=='-') ch=getchar(),fh=-1;
	else fh=1;
	while(ch>='0'&&ch<='9') x=(x<<1)+(x<<3)+ch-'0',ch=getchar();
	x*=fh;
}

int n;
int x[1007],y[1007],w[1007];
int sx,sy;

double ansx,ansy,ans=1e18,T;
double delta=0.993;

double eps=0.00000000001;

double calc(double xxx,double yyy){
	double res=0.0;
	for(int i=1;i<=n;i++){
		double xx=xxx-x[i],yy=yyy-y[i];
		res=res+sqrt(xx*xx+yy*yy)*w[i];
	}
	return res;
}

double SA(){
	double nx=ansx,ny=ansy;
	T=2000;
	while(T>eps){
		double mx=nx+((rand()*2-RAND_MAX))*T,my=ny+(rand()*2-RAND_MAX)*T;
		double na=calc(mx,my);double del=na-ans;
		if(del<0){
			ansx=nx=mx,ansy=ny=my;
			ans=na;
		}
		else{
			if(exp(-del/T)*RAND_MAX>rand()) nx=mx,ny=my;
		}
		T*=delta;
	}
}

int ss,sss;

int main(){
	srand(192**817);
	read(n);
	for(int i=1;i<=n;i++){
		read(x[i]);read(y[i]);read(w[i]);
		ss+=x[i],sss+=y[i];
	}
	ansx=(double)ss/n;ansy=(double)sss/n;
	SA();SA();SA();SA();//SA();//SA();SA();SA();SA();SA();SA();
//	SA();SA();SA();SA();SA();SA();SA();SA();SA();SA();SA();
	printf("%.3f %.3f
",ansx,ansy);
	return 0;
}