stations.cpp: In function 'std::vector<int> label(int, int, std::vector<int>, std::vector<int>)':
stations.cpp:35:21: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
35 | for (int i = 0; i < u.size(); i++) {
| ~~^~~~~~~~~~
stations.cpp:36:9: warning: unused variable 'a' [-Wunused-variable]
36 | int a = u[i], b = v[i];
| ^
stations.cpp:36:19: warning: unused variable 'b' [-Wunused-variable]
36 | int a = u[i], b = v[i];
| ^
stations.cpp: In function 'int find_next_station(int, int, std::vector<int>)':
stations.cpp:51:21: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
51 | for (int i = 0; i < c.size(); i++) {
| ~~^~~~~~~~~~
stations.cpp:55:1: warning: control reaches end of non-void function [-Wreturn-type]
55 | }
| ^