【模板】BFS

#include <stdio.h>  #include <string.h>  #include <queue>  using namespace std;    struct node  {      int x,y,step;  };    char map[105][105];  int vis[105][105];  int to[4][2]= {1,0,-1,0,0,1,0,-1};  int n,m,sx,sy,ex,ey,ans;    int check(int x,int y)  {      if(x<0 || x>=n || y<0 || y>=m)          return 1;      if(vis[x][y] || map[x][y]=='#')          return 1;      return 0;  }    void bfs()  {      int i;      queue<node> Q;      node a,next;      a.x = sx;      a.y = sy;      a.step = 0;      vis[a.x][a.y]=1;      Q.push(a);      while(!Q.empty())      {          a = Q.front();          Q.pop();          if(map[a.x][a.y]=='E')          {              ans = a.step;              return ;          }          for(i = 0; i<4; i++)          {              next = a;              next.x+=to[i][0];              next.y+=to[i][1];              if(check(next.x,next.y))                  continue;              next.step=a.step+1;              vis[next.x][next.y] = 1;              Q.push(next);          }      }      ans = -1;  }    int main()  {      int t;      scanf("%d",&t);      while(t--)      {          scanf("%d%d",&n,&m);          int i,j;          for(i = 0; i<n; i++)              scanf("%s",map[i]);          for(i = 0; i<n; i++)          {              for(j = 0; j<m; j++)              {                  if(map[i][j]=='S')                  {                      sx = i;                      sy = j;                  }              }          }          memset(vis,0,sizeof(vis));          bfs();          printf("%d\n",ans);      }        return 0;  }