【bzoj2709】 迷宫花园 spfa

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<iostream>
#include<algorithm>
#define maxn 210
#define eps 1e-7
#define inf 1000000000

using namespace std;

double dis[40010];
int dx[4]={0,0,1,-1};
int dy[4]={1,-1,0,0};
int a[maxn][maxn];
bool vis[40010];
int next[200010],to[200010],head[40010],q[40010];
double len[200010];
int num,n,m,cnt,s,t,T;
double L;

void addedge(int x,int y,double z)
{
	num++;to[num]=y;len[num]=z;next[num]=head[x];head[x]=num;
}

double calc(double x)
{
	memset(head,0,sizeof(head));
	num=0;
	for (int i=1;i<=n;i++)
	  for (int j=1;j<=m;j++)
	    if (a[i][j])
	    {
	    	for (int k=0;k<2;k++) 
	    	  if (a[i+dx[k]][j+dy[k]]) addedge(a[i][j],a[i+dx[k]][j+dy[k]],1);
	    	for (int k=2;k<4;k++)
	    	  if (a[i+dx[k]][j+dy[k]]) addedge(a[i][j],a[i+dx[k]][j+dy[k]],x);
	    }
	memset(vis,0,sizeof(vis));
	for (int i=1;i<=cnt;i++) dis[i]=inf;
	int l=0,r=1;
	q[1]=s;vis[s]=1;dis[s]=0;
	while (l!=r)
	{
		l++;if (l==40000) l=0;
		int x=q[l];
		for (int p=head[x];p;p=next[p])
		  if (dis[x]+len[p]<dis[to[p]])
		  {
		  	dis[to[p]]=dis[x]+len[p];
		  	if (!vis[to[p]])
		  	{
		  		r++;if (r==40000) r=0;
		  		q[r]=to[p];vis[to[p]]=1;
		  	}
		  }
		vis[x]=0;
	}
	return dis[t];
}

int main()
{
	scanf("%d",&T);
	while (T--)
	{
		scanf("%lf%d%d",&L,&n,&m);
		memset(a,0,sizeof(a));
		cnt=0;
		for (int i=1;i<=n;i++)
		{
			char c;
			scanf("%c",&c);
			while (c!='\n') scanf("%c",&c);
			for (int j=0;j<m;j++)
			{
				scanf("%c",&c);
				while (c=='\n') scanf("%c",&c);
			  	if (c==' ') a[i][j+1]=++cnt;
			  	if (c=='S') a[i][j+1]=++cnt,s=cnt;
			  	if (c=='E') a[i][j+1]=++cnt,t=cnt;
			}
		}
		double l=0,r=11,ans=0;
		while ((r-l)>eps)
		{
			double mid=(l+r)/2.0;
			if (calc(mid)>=L) ans=mid,r=mid; else l=mid;
		}
		printf("%.5lf\n",ans);
	}
	return 0;
}