/in/foo.cc: In function 'int main()':
/in/foo.cc:7:26: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
    7 |         for(int len=1;len<=st.size();len++)
      |                       ~~~^~~~~~~~~~~
/in/foo.cc:10:36: 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 si=0;si+len<=st.size()&&f;si++)//枚举起始位置
      |                              ~~~~~~^~~~~~~~~~~
/in/foo.cc:13:43: warning: comparison of integer expressions of different signedness: 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} and 'int' [-Wsign-compare]
   13 |                         if(st.find(b,si+1)!=-1)//比右边更好
      |                            ~~~~~~~~~~~~~~~^~~~