/in/foo.cc: In function 'int main()':
/in/foo.cc:10:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   10 |         for(int i=1;i<=goal.size()-1;i++)
      |                     ~^~~~~~~~~~~~~~~
/in/foo.cc:12:26: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   12 |         for(int len=2;len<=goal.size()-1;len++)//长度
      |                       ~~~^~~~~~~~~~~~~~~
/in/foo.cc:13:30: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   13 |                 for(int i=1;i<=goal.size()-len;i++)//起点i
      |                             ~^~~~~~~~~~~~~~~~~