BZOJ 2709 迷宫花园

直接二分这个v。

#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cstring>
#include<queue>
#include<cmath>
#define maxn 150
#define maxv 10050
#define eps 1e-7
#define inf 2147483
using namespace std;
int t,n,m,map[maxn][maxn],bx,by,ex,ey;
int dx[]={0,1,-1,0,0},dy[]={0,0,0,1,-1};
double l,dis[maxn][maxn],lefts,rights;
char s[maxn];
bool vis[maxn][maxn];
queue <int> q;
bool judge(int x,int y)
{
    if ((x>=1) && (x<=n) && (y>=1) && (y<=m) && (map[x][y]))
        return true;
    return false;
}
double spfa(double x)
{
    while (!q.empty()) q.pop();
    for (int i=1;i<=n;i++)
        for (int j=1;j<=m;j++)
            vis[i][j]=false,dis[i][j]=inf;
    q.push(bx);q.push(by);vis[bx][by]=true;dis[bx][by]=0;
    while (!q.empty())
    {
        int hx,hy;
        hx=q.front();q.pop();hy=q.front();q.pop();
        for (int i=1;i<=2;i++)
        {
            int nx=hx+dx[i],ny=hy+dy[i];
            if ((judge(nx,ny) && (dis[nx][ny]>dis[hx][hy]+x)))
            {
                dis[nx][ny]=dis[hx][hy]+x;
                if (!vis[nx][ny])
                {
                    vis[nx][ny]=true;
                    q.push(nx);q.push(ny);
                }
            }
        }
        for (int i=3;i<=4;i++)
        {
            int nx=hx+dx[i],ny=hy+dy[i];
            if ((judge(nx,ny) && (dis[nx][ny]>dis[hx][hy]+1)))
            {
                dis[nx][ny]=dis[hx][hy]+1;
                if (!vis[nx][ny])
                {
                    vis[nx][ny]=true;
                    q.push(nx);q.push(ny);
                }
            }
        }
        vis[hx][hy]=false;
    }
    return dis[ex][ey];
}
void work()
{
    scanf("%lf%d%d
",&l,&n,&m);
    for (int i=1;i<=n;i++)
    {
        gets(s);
        for (int j=0;j<m;j++)
        {
            if (s[j]=='#') map[i][j+1]=0;
            else if (s[j]==' ') map[i][j+1]=1;
            else if (s[j]=='S') {bx=i;by=j+1;map[bx][by]=1;}
            else {ex=i;ey=j+1;map[ex][ey]=1;}
        }
    }
    lefts=0;rights=10;double ans,ret;
    while (rights-lefts>eps)
    {
        double mid=(lefts+rights)/2;
        ans=spfa(mid);ret=mid;
        if (ans>=l) rights=mid;
        else lefts=mid;
    }
    printf("%.5lf
",ret);
}
int main()
{
    scanf("%d",&t);
    for (int i=1;i<=t;i++)
        work();
    return 0;
}