/in/foo.cc: In function 'std::vector<int> subct(std::vector<int>&, std::vector<int>&)':
/in/foo.cc:21:18: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   21 | for(int i = 0; i < A.size(); i++){ //从低位开始相减
      |                ~~^~~~~~~~~~
/in/foo.cc:23:5: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   23 | if(i<B.size()) t-=B[i];
      |    ~^~~~~~~~~