/in/foo.cc: In constructor 'BinTree::BinTree(char*, char*)':
/in/foo.cc:49:42: error: 'strlen' was not declared in this scope
  int ipre = 0, imid = 0, len = strlen(pre);
                                          ^
/in/foo.cc: In function 'int main()':
/in/foo.cc:106:30: warning: ISO C++ forbids converting a string constant to 'char*' [-Wwrite-strings]
  BinTree T("abdecf", "dbeacf");
                              ^
/in/foo.cc:106:30: warning: ISO C++ forbids converting a string constant to 'char*' [-Wwrite-strings]