foo.cc: In function ‘void tarjan(int, int)’:
foo.cc:12:22: warning: comparison of integer expressions of different signedness: ‘int’ and ‘std::vector<edge>::size_type’ {aka ‘long unsigned int’} [-Wsign-compare]
   12 |     for(int i = 0; i < E[u].size(); ++i) {
      |                    ~~^~~~~~~~~~~~~
foo.cc: In function ‘void dfs(int, int)’:
foo.cc:31:22: warning: comparison of integer expressions of different signedness: ‘int’ and ‘std::vector<edge>::size_type’ {aka ‘long unsigned int’} [-Wsign-compare]
   31 |     for(int i = 0; i < E[u].size(); ++i) {
      |                    ~~^~~~~~~~~~~~~
foo.cc: In function ‘int main()’:
foo.cc:77:26: warning: comparison of integer expressions of different signedness: ‘int’ and ‘std::vector<edge>::size_type’ {aka ‘long unsigned int’} [-Wsign-compare]
   77 |         for(int i = 0; i < E[u].size(); ++i) {
      |                        ~~^~~~~~~~~~~~~
foo.cc:78:17: warning: unused variable ‘v’ [-Wunused-variable]
   78 |             int v = E[u][i].to, id = E[u][i].id;
      |                 ^