foo.cc: In function 'int main()':
foo.cc:11:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for(int i = 0; i < str.size(); i++)
                        ~~^~~~~~~~~~~~

正在同步测试数据，请稍后
自豪的采用HydroJudge(https://github.com/hydro-dev/Hydro)进行评测。