foo.cpp:60:22: error: '_TCHAR' has not been declared
 int _tmain(int argc, _TCHAR* argv[])
                      ^
foo.cpp: In function 'int _tmain(int, int**)':
foo.cpp:64:30: error: 'memset' was not declared in this scope
  memset(used, 0, sizeof(used));
                              ^