hdu 1242 Rescue（bfs）

此刻再看优先队列，不像刚接触时的那般迷茫！这也许就是集训的成果吧！

加油！！！优先队列必须要搞定的！

这道题意很简单！自己定义优先级别！

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#include<stdio.h>

#include<string.h>
#include<queue>

using namespace std;

int n,m,dir[4][2]={1,0,0,1,-1,0,0,-1};

char s[1010][1010];

struct node

{


int x,y,step;


friend bool operator<(node a,node b)


{


return a.step>b.step;


}


/*


bool operator<(const node &b) const


{


return step>b.step;


}*/

};

bool judge(int x,int y)

{


if(x>=0&&x<n&&y>=0&&y<m&&s[x][y]!='#')


return true;


return false;

}

int bfs(int x0,int y0)

{


int k,x,y;


priority_queue<node>q;


node cur,next;


cur.x=x0;cur.y=y0;cur.step=0;


q.push(cur);


s[x0][y0]='#';


while(!q.empty())


{


cur=q.top();


q.pop();


for(k=0;k<4;k++)


{


x=next.x=cur.x+dir[k][0];


y=next.y=cur.y+dir[k][1];


next.step=cur.step+1;


if(judge(x,y))


{


if(s[x][y]=='r')


return next.step;


else if(s[x][y]=='.')


q.push(next);


else


{


next.step++;


q.push(next);


}


s[x][y]='#';


}


}


}


return -1;

}

int main()

{


int i,j,x,y,ans;


while(scanf("%d%d",&n,&m)!=EOF)


{


for(i=0;i<n;i++)


scanf("%s",s[i]);


for(i=0;i<n;i++)


{


for(j=0;j<m;j++)


if(s[i][j]=='a')


{


x=i;y=j;


}


if(j<m)


break;


}


ans=bfs(x,y);


if(ans==-1)


printf("Poor ANGEL has to stay in the prison all his life.\n");


else


printf("%d\n",ans);


}


return 0;

}

题目链接：http://acm.hdu.edu.cn/showproblem.php?pid=1242