P2503 [HAOI2006]均分数据

Archie

怎样用模拟退火搞序列

随机交换就可以了

dp检查

#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cmath>
#include<cstring>
using namespace std;
int n,m;int a[50],na[50];
double t;double ans=1e18;
double delat=0.996;
double dp[50][50];
double sum[50];
double work(){
	memset(dp,0x7f,sizeof(dp));
	dp[0][0]=0;
	sum[1]=na[1];
	for(int i=2;i<=n;++i)
	sum[i]=sum[i-1]+na[i];
	for(int i=1;i<=n;++i){
		for(int j=1;j<=min(m,i);++j){
			for(int z=0;z<i;++z){
				dp[i][j]=min(dp[i][j],dp[z][j-1]+((sum[i]-sum[z])-sum[n]/m)*((sum[i]-sum[z])-sum[n]/m));
			}	
		} 
	}
	return dp[n][m];
}
void sa(){
	double nans=ans;
	for(int i=1;i<=n;++i){
		na[i]=a[i];
	}
	t=2000;
	while(t>1e-15){
		int nx=rand()%n+1;
		int ny=rand()%n+1;
		if(nx==ny)
		 continue;
		swap(na[nx],na[ny]);
		double res=work();
		//cout<<res<<endl;
		double key=res-nans;
		if(key<0){
			nans=res;
			ans=res;
			for(int i=1;i<=n;++i){
				a[i]=na[i];
			}
		}else{
			if(exp(-res/delat)*RAND_MAX<rand())
			swap(na[nx],na[ny]);
			else
			nans=res;
		}
		t*=delat;
	}
}
int main(){
	srand(20040519);
	srand(rand());
	scanf("%d%d",&n,&m);
	for(int i=1;i<=n;++i){
		scanf("%d",&a[i]);
	} 
	for(int i=1;i<=6;++i){
		sa();
		//printf("%.2lf
",ans);
	}
	printf("%.2lf",sqrt(ans/m));
	return 0;
}