stations.cpp: In function 'void dfs(int)':
stations.cpp:21:15: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
21 | for(int i=0;i<v[N].size();i++)
| ~^~~~~~~~~~~~
stations.cpp: In function 'std::vector<int> label(int, int, std::vector<int>, std::vector<int>)':
stations.cpp:37:15: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
37 | for(int i=0;i<a.size();i++)
| ~^~~~~~~~~
stations.cpp: In function 'int find_next_station(int, int, std::vector<int>)':
stations.cpp:52:16: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
52 | for(int i=0;i<c.size();i++)
| ~^~~~~~~~~
stations.cpp:61:16: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
61 | for(int i=0;i<c.size();i++)
| ~^~~~~~~~~
stations.cpp:71:9: warning: 're' may be used uninitialized in this function [-Wmaybe-uninitialized]
71 | return re;
| ^~