foo.cc: In function ‘int main()’:
foo.cc:52:23: warning: comparison of integer expressions of different signedness: ‘int’ and ‘std::vector<Node>::size_type’ {aka ‘long unsigned int’} [-Wsign-compare]
   52 |         for (i = 0; i < v.size(); i++)
      |                     ~~^~~~~~~~~~
foo.cc:60:15: warning: comparison of integer expressions of different signedness: ‘int’ and ‘std::vector<Node>::size_type’ {aka ‘long unsigned int’} [-Wsign-compare]
   60 |         if (i >= v.size())
      |             ~~^~~~~~~~~~~