foo.cc: In function 'int trans(std::string, std::string)':
foo.cc:10:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   10 |         for(int i=0; i<s.size(); i++)
      |                      ~^~~~~~~~~
foo.cc:12:24: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   12 |                 while(j<t.size() && t[j] != '1') j++;
      |                       ~^~~~~~~~~
foo.cc:7:13: warning: unused variable 'i' [-Wunused-variable]
    7 |         int i=0, j=0;
      |             ^

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