1643. Attack of the Dark Fortress 夜

http://acm.timus.ru/problem.aspx?space=1&num=1643

bfs 就可以 不过要注意细节

思路：

分别求出 ‘！’到每个点的最短路 dist1 ，‘$’到每个点的最短路 dist2  和 ‘*’到每个点的最短路 dist3

然后枚举每个点 的 max(dist1+dist2)+dist3 值 求最小

代码：

#include<iostream>
#include<stdio.h>
#include<string.h>
#include<math.h>
#include<algorithm>
#include<vector>
#include<set>
#include<map>
#include<string>
#include<queue>
#include<stack>
#include <iomanip>
using namespace std;
#define LL long long
const int INF=0x3f3f3f3f;
const int N=105;
char graph[N][N];
typedef pair<int,int>point;
int X[]={0,0,1,1,1,-1,-1,-1};
int Y[]={-1,1,1,0,-1,-1,0,1};
vector<point>tran[27];
int n,m;
void bfs(int stx,int sty,int dist[N][N])
{
    queue<point>qt;
    qt.push(point(stx,sty));
    dist[stx][sty]=0;
    while(!qt.empty())
    {
        int x=(qt.front()).first;
        int y=(qt.front()).second;
        qt.pop();
        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&&graph[l1][l2]!='#'&&graph[l1][l2]!='*'&&dist[l1][l2]==-1)
            {
                dist[l1][l2]=dist[x][y]+1;
                qt.push(point(l1,l2));
                if(graph[l1][l2]>='A'&&graph[l1][l2]<='Z')
                {

                    for(unsigned int i=0;i<tran[graph[l1][l2]-'A'].size();++i)
                    {
                        int t1=tran[graph[l1][l2]-'A'][i].first;
                        int t2=tran[graph[l1][l2]-'A'][i].second;;
                        if(dist[t1][t2]==-1)
                        {
                            dist[t1][t2]=dist[l1][l2];
                            qt.push(point(t1,t2));
                        }
                    }
                }
            }
        }
    }/*
    for(int i=0;i<n;++i)
    {
        for(int j=0;j<m;++j)
        cout<<dist[i][j]<<" ";
        cout<<endl;
    }cout<<endl;*/
}
int main()
{
    //freopen("data.in","r",stdin);
    int dist1[N][N];
    int dist2[N][N];
    int dist3[N][N];
    while(cin>>n>>m)
    {
        getchar();
        for(int i=0;i<n;++i)
        gets(graph[i]);
        memset(dist1,-1,sizeof(dist1));
        memset(dist2,-1,sizeof(dist2));
        memset(dist3,-1,sizeof(dist3));
        for(int i=0;i<27;++i)
        tran[i].clear();
        for(int i=0;i<n;++i)
        for(int j=0;j<m;++j)
        if(graph[i][j]>='A'&&graph[i][j]<='Z')
        {tran[graph[i][j]-'A'].push_back(point(i,j));}
        for(int i=0;i<n;++i)
        for(int j=0;j<m;++j)
        {
            if(graph[i][j]=='$')
            bfs(i,j,dist1);
            else if(graph[i][j]=='!')
            bfs(i,j,dist2);
            else if(graph[i][j]=='*')
            bfs(i,j,dist3);
        }
        int ans=INF;
        for(int i=0;i<n;++i)
        for(int j=0;j<m;++j)
        {
            if(dist1[i][j]>=0&&dist2[i][j]>=0&&dist3[i][j]>=0)
            {
                ans=min(ans,max(dist1[i][j],dist2[i][j])+dist3[i][j]);
            }
        }
        if(ans==INF)
        cout<<"Impossible"<<endl;
        else
        cout<<ans<<endl;
    }
    return 0;
}