foo.cc: In function ‘int main()’:
foo.cc:11:30: warning: comparison of integer expressions of different signedness: ‘int’ and ‘std::__cxx11::basic_string<char>::size_type’ {aka ‘long unsigned int’} [-Wsign-compare]
   11 |         while (idx != -1&&idx<t.size())
      |                           ~~~^~~~~~~~~