foo.cc: In function 'std::vector<int> mul(std::vector<int>&, int)':
foo.cc:10:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   10 |     for (int i = 0; i < a.size() || t; i++)
      |                     ~~^~~~~~~~~~
foo.cc:12:15: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   12 |         if (i < a.size()) t += a[i] * b;
      |             ~~^~~~~~~~~~
foo.cc: In function 'std::vector<int> add(std::vector<int>&, std::vector<int>&)':
foo.cc:25:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   25 |     for (int i = 0; i < a.size(); i++)
      |                     ~~^~~~~~~~~~
foo.cc:28:15: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   28 |         if (i < b.size()) t += b[i];
      |             ~~^~~~~~~~~~
foo.cc: In function 'int main()':
foo.cc:47:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   47 |     for (int i = 0; i < a1.size(); i++)
      |                     ~~^~~~~~~~~~~
foo.cc:55:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   55 |     for (int i = 0; i < a2.size(); i++)
      |                     ~~^~~~~~~~~~~

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