bnuoj 25662 A Famous Grid (构图+BFS)

http://www.bnuoj.com/bnuoj/problem_show.php?pid=25662

 #include <iostream>
 #include <stdio.h>
 #include <string.h>
 #include <math.h>
 #include <algorithm>
 #include <stack>
 #include <queue>

 #define N 150
 using namespace std;

 struct Nod
 {
     int x,y,step;
 }node[];

 int map[N][N];
 int mark[N][N];
 int prim[];

 int cx[]={,,-,};
 int cy[]={,,,-};

 int cnt=;

 void getMap(int x,int y,int re)
 {
     while()
     {
         int dx,dy;
         dx = x + cx[(re+)%];
         dy = y + cy[(re+)%];
         if(!(dx>=&&dx<N&&dy>=&&dy<N))
         {
             break;
         }
         if(map[dx][dy]==)
         {
             map[dx][dy]= ++cnt;
             node[cnt].x = dx;
             node[cnt].y = dy;
           //  getMap(dx,dy,(re+1)%4);
             x = dx;
             y = dy;
             re = (re+)%;
         }
         else
         {
             dx = x + cx[re%];
             dy = y + cy[re%];
             if(!(dx>=&&dx<N&&dy>=&&dy<N))
             {
                 break ;
             }
             map[dx][dy]= ++cnt;
             node[cnt].x = dx;
             node[cnt].y = dy;
            // getMap(dx,dy,re);
             x = dx;
             y = dy;
         }
     }
 }

 int bfs(int x,int y)
 {
     memset(mark,,sizeof(mark));
     queue<Nod> Q;
     Nod temp;
     temp.x = node[x].x;
     temp.y = node[x].y;
     temp.step = ;
     Q.push(temp);
     mark[temp.x][temp.y] = ;
     while(!Q.empty())
     {
         Nod td = Q.front();
         Q.pop();
         if(td.x==node[y].x&&td.y==node[y].y)
         {
             return td.step;
         }
         int i;
         for(i=;i<;i++)
         {
             temp.x = td.x + cx[i];
             temp.y = td.y + cy[i];
             temp.step = td.step + ;
             if(map[temp.x][temp.y]>=&&map[temp.x][temp.y]<=&&prim[map[temp.x][temp.y]]&&!mark[temp.x][temp.y])
             {
                 mark[temp.x][temp.y]=;
                 Q.push(temp);
             }
         }
     }
     return -;
 }

 int main()
 {
     cnt=;
     int cas=;
     map[][]=;
     getMap(,,);
     node[].x = ;
     node[].y = ;
    // cout<<cnt<<endl;
     int i,j;
     prim[]=;
     for(i=;i<;i++)
     {
         for(j=;j*j<=i;j++)
         {
             if(i%j==)
             {
                 prim[i]=;
                 break;
             }
         }
     }
  //   for(i=1;i<=100;i++)
    // if(!prim[i])cout<<i<<" ";

     int x,y;
     while(~scanf("%d%d",&x,&y))
     {
         printf("Case %d: ",cas++);
         int ans = bfs(x,y);
         if(ans==-)
         {
             puts("impossible");
         }
         else
         {
             printf("%d\n",ans);
         }
     }

     return ;
 }