foo.cc: In function ‘void dfs(int, int)’:
foo.cc:14:22: warning: comparison of integer expressions of different signedness: ‘int’ and ‘std::vector<int>::size_type’ {aka ‘long unsigned int’} [-Wsign-compare]
   14 |     for(int i = 0; i < g[x].size(); i ++) {
      |                    ~~^~~~~~~~~~~~~