1254. Die Hard 夜

http://acm.timus.ru/problem.aspx?space=1&num=1254

刚开始想多了 依次spfa就可以

代码：

#include<iostream>
#include<cstdio>
#include<cstring>
#include<string>
#include<map>
#include<vector>
#include<stack>
#include<set>
#include<map>
#include<queue>
#include<algorithm>
#include<cmath>
#define LL long long
#define sint short int
//#pragma comment(linker, "/STACK:1024000000,1024000000")
using namespace std;

const int N=1005;
const int INF=0x7fffffff;
typedef pair<int,int>point;
int X[]={-1,-1,-1,0,0,1,1,1};
int Y[]={-1,0,1,-1,1,-1,0,1};
double L[]={sqrt(2.0),1.0,sqrt(2.0),1.0,1.0,sqrt(2.0),1.0,sqrt(2.0)};
point p[N];
char s[N][N];
bool in[N][N];
double dist[N][N];
void init(int n,int k)
{
    getchar();
    for(int i=0;i<n;++i)
    gets(s[i]);
    for(int i=0;i<=k;++i)
    {
       scanf("%d %d",&p[i].second,&p[i].first);
        --p[i].first;--p[i].second;
    }
}
double spfa(int n,int m,int x1,int y1,int x2,int y2)
{
    memset(in,false,sizeof(in));
    for(int i=0;i<n;++i)
    for(int j=0;j<m;++j)
    dist[i][j]=-1.0;
    queue<int>qtx,qty;
    dist[x1][y1]=0.0;
    in[x1][y1]=true;
    qtx.push(x1);
    qty.push(y1);
    while(!qtx.empty())
    {
        int x=qtx.front();qtx.pop();
        int y=qty.front();qty.pop();
        in[x][y]=false;
        for(int i=0;i<8;++i)
        {
            int l1=x+X[i];
            int l2=y+Y[i];
            if(l1>=0&&l1<n&&l2>=0&&l2<m&&s[l1][l2]=='.')
            {
                if(dist[l1][l2]<0.0||dist[l1][l2]>dist[x][y]+L[i])
                {
                    dist[l1][l2]=dist[x][y]+L[i];
                    if(!in[l1][l2])
                    {
                        in[l1][l2]=true;
                        qtx.push(l1);
                        qty.push(l2);
                    }
                }
            }
        }
    }
    return dist[x2][y2];
}
double solve(int n,int m,int k)
{
    double sum=0;
    int l=0,r=1;
    while(r<=k)
    {
        double tmp=spfa(n,m,p[l].first,p[l].second,p[r].first,p[r].second);
        //cout<<tmp<<endl;
        if(tmp<=0)
        ++r;
        else
        {l=r;++r;sum+=tmp;}
    }
    return sum;
}
int main()
{
    //freopen("data.in","r",stdin);
    int n,m,k;
    double v;
    while(cin>>m>>n>>k>>v)
    {
        init(n,k);
        printf("%.2lf\n",solve(n,m,k)/v);
    }
}