foo.cc: In function 'int main()':
foo.cc:11:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   11 |         for (i = 0; i < s.length(); i++) {
      |                     ~~^~~~~~~~~~~~
foo.cc:13:35: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   13 |                 for (j = i + 1; j < s.length(); j++) {
      |                                 ~~^~~~~~~~~~~~
foo.cc:17:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   17 |                 if (j == s.length())
      |                     ~~^~~~~~~~~~~~~

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