/in/foo.cc: In member function 'Node* Bintree::Create(char*, int, char*, int, int)':
/in/foo.cc:32:46: error: 'i' was not declared in this scope
   p->lchild = Create(pre, ipre+1, mid, imid, i);
                                              ^
/in/foo.cc: In function 'int main()':
/in/foo.cc:55:20: error: 'strlen' was not declared in this scope
  int n = strlen(pre);
                    ^