/in/foo.cc: In function 'int main()':
/in/foo.cc:19:15: warning: 'root' may be used uninitialized in this function [-Wmaybe-uninitialized]
   f[k][1]=da[k];       
           ~~~~^
/in/foo.cc:70:6: note: 'root' was declared here
  int root;
      ^~~~