1254. Die Hard

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);

    }

}