POJ3669 Meteor Shower BFS

#include<iostream>
#include<queue>
using namespace std;
#define MAXN 302
struct point{
        int x,y;
};
int dir[4][2]={{-1,0},{0,1},{1,0},{0,-1}};
int map[MAXN][MAXN];
bool visted[MAXN][MAXN];
int steps;
void bfs()
{
          queue<point> Q;
          point p1={0,0},p2;
          int i;
          int t=1,count1=0,count2=0;// count用来计算steps
          Q.push(p1);
          visted[0][0]=true;
          while(!Q.empty())
          {
                   if(count1>count2)
                           steps++,count2=t-1;
                   p1=Q.front();
                   Q.pop();
                   count1++;
                   for(i=0;i<4;i++)
                   {
                             p2=p1;
                             p2.x+=dir[i][0];
                             p2.y+=dir[i][1];
                             if(p2.x>=0&&p2.x<=MAXN-1&&p2.y>=0&&p2.y<=MAXN-1)
                             {
                                     if(map[p2.x][p2.y]==0x7fffffff)
                                      {
                                      steps++;return;
                                      }  
                                     if(visted[p2.x][p2.y]==false&&steps+1<map[p2.x][p2.y])
                                     {visted[p2.x][p2.y]=true;Q.push(p2);t++;}
                             }
                   }
          }
                             
                          
          steps=-1;
}                
int main()
{
         int i,j,m;
         cin>>m;
         for(i=0;i<MAXN;i++)
            for(j=0;j<MAXN;j++)
                    map[i][j]=0x7fffffff,visted[i][j]=false;
         for(i=0;i<m;i++)
         {
                 int x,y,t;
                 scanf("%d %d %d",&x,&y,&t);
                 if(map[x][y]>t)map[x][y]=t;
                 if(map[x+1][y]>t)map[x+1][y]=t;
                 if(map[x][y+1]>t)map[x][y+1]=t;
                 if(x-1>=0&&map[x-1][y]>t)map[x-1][y]=t;
                 if(y-1>=0&&map[x][y-1]>t)map[x][y-1]=t;
         }
         steps=0;
         if(map[0][0]!=0x7fffffff)
                bfs();
         cout<<steps<<endl;

         return 0;
}