/in/foo.c: In function 'dfs':
/in/foo.c:25:13: error: expected identifier or '(' before '&' token
         int &a=tree[i];//取该层一个结点
             ^
/in/foo.c: In function 'main':
/in/foo.c:58:5: warning: this 'for' clause does not guard... [-Wmisleading-indentation]
     for(i=1;i<=p;i++)
     ^~~
/in/foo.c:60:2: note: ...this statement, but the latter is misleadingly indented as if it is guarded by the 'for'
  printf("%d\n",count);
  ^~~~~~