/in/foo.cc: In function 'void fanzhuan(char*)':
/in/foo.cc:35:19: error: 'strlen' was not declared in this scope
  int na = strlen(a), tem = 0;
                   ^
/in/foo.cc:39:3: error: 'tem' was not declared in this scope
   tem = a[left];
   ^~~
/in/foo.cc: In function 'void Add(char*, char*, char*)':
/in/foo.cc:52:19: error: 'strlen' was not declared in this scope
  int na = strlen(a);
                   ^