foo.cc: In function 'std::vector<int> mul(std::vector<int>&, int)':
foo.cc:12:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   12 |     for (int i = 0; i < A.size() || t; i ++ )
      |                     ~~^~~~~~~~~~
foo.cc:14:15: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   14 |         if (i < A.size()) t += A[i] * b;
      |             ~~^~~~~~~~~~

[Hydro](https://hydro.ac)提供评测服务