foo.cc: In function 'int match1(std::string&)':
foo.cc:9:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
    9 |     for (int i = 0; i < s.size(); i++)
      |                     ~~^~~~~~~~~~
foo.cc: In function 'int match2(std::string&)':
foo.cc:25:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   25 |     for (int i = 0; i < s.size(); i++)
      |                     ~~^~~~~~~~~~
foo.cc: In function 'int main()':
foo.cc:45:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   45 |     for (int i = 0; i < s.size(); i++)
      |                     ~~^~~~~~~~~~

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