hdu 2822 Dogs（优先队列）

#include<stdio.h>
#include<string.h>
#include<queue>
#include<algorithm>
#define N 1005
using namespace std;
char map

;
int v

,d[4][2] = { {-1,0},{1,0},{0,-1},{0,1} };
int begin_x,begin_y,end_x,end_y,n,m;
struct node
{
int x,y,step;
friend bool operator < (node a,node b)
{
return a.step > b.step;
}
};
void bfs()
{
memset(v,0,sizeof(v));
priority_queue <node> q;
node s,temp;
s.x = begin_x;
s.y = begin_y;
s.step = 0;
v[s.x][s.y] = 1;
q.push(s);
while(!q.empty())
{
temp = q.top();
q.pop();
if(s.x == end_x && s.y == end_y)
{
printf("%d\n",s.step);
return ;
}
for(int i= 0 ; i < 4 ; i ++)
{
s = temp;
s.x += d[i][0];
s.y += d[i][1];
if(s.x < 0 || s.x >= n || s.y < 0 || s.y >= m || v[s.x][s.y])
continue;
v[s.x][s.y] = 1;
if(map[s.x][s.y] == '.') s.step ++;
q.push(s);
}
}
}
int main()
{
int i;
while(scanf("%d%d",&n,&m) && (n + m))
{
for(i = 0 ; i < n ; i ++)
scanf("%s",map[i]);
scanf("%d%d%d%d",&begin_x,&begin_y,&end_x,&end_y);
begin_x -- ; begin_y --; end_x -- ; end_y --;//题目给出的坐标都是从1开始计算的
bfs();
}
return 0;
}