HDU 1026

http://acm.hdu.edu.cn/showproblem.php?pid=1026

记录bfs路径，用一个数组记录next前驱的方向，然后递归的时候减回去即可

#include <iostream>
#include <cstdio>
#include <cstring>
#include <queue>

using namespace std ;
const int INF=0xfffffff;

int n,m;
char M[105][105];

struct node{
    int x,y,step;
    friend bool operator <(node a,node b){
        return a.step>b.step;
    }
};

int dx[]={1,-1,0,0};
int dy[]={0,0,1,-1};
int vis[105][105];

int rd[105][105];

int bfs(){
    memset(vis,0,sizeof(vis));
    priority_queue <node> q;
    node s;
    s.x=0;s.y=0;s.step=0;
    if(M[0][0]!='X' && M[n-1][m-1]!='X')q.push(s);
    while(!q.empty()){
        node u=q.top();
        q.pop();
        if(u.x==n-1 && u.y==m-1)return u.step;
        for(int i=0;i<4;i++){
            int xx=u.x+dx[i];
            int yy=u.y+dy[i];
            if(xx<0 || xx>=n || yy<0 || yy>=m)continue;
            if(M[xx][yy]=='X')continue;
            if(vis[xx][yy])continue;
            vis[xx][yy]=1;
            node next=u;
            next.x=xx;next.y=yy;next.step++;
            if(M[xx][yy]>='1' && M[xx][yy]<='9')
                next.step+=(M[xx][yy]-'0');
            rd[xx][yy]=i;
            q.push(next);
        }
    }
    return INF;
}
int tt;
void output(int x,int y){
    if(rd[x][y]==-1)return;
    int xx=x-dx[rd[x][y]];
    int yy=y-dy[rd[x][y]];
    output(xx,yy);
    printf("%ds:(%d,%d)->(%d,%d)
",tt++,xx,yy,x,y);
    if(M[x][y]>='1' && M[x][y]<='9'){
        int nn=M[x][y]-'0';
        while(nn--){
            printf("%ds:FIGHT AT (%d,%d)
",tt++,x,y);
        }
    }
}

int main(){
    while(~scanf("%d%d",&n,&m)){
        for(int i=0;i<n;i++)    
            scanf("%s",M[i]);
           int ans=bfs();
           if(ans==INF)puts("God please help our poor hero.");
           else{
               printf("It takes %d seconds to reach the target position, let me show you the way.
",ans);
            rd[0][0]=-1;
            tt=1;
            output(n-1,m-1);
           }
           puts("FINISH");
    }
    return 0;
}