cities.cpp:11:1: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
11 | main() {
| ^~~~
cities.cpp: In function 'int main()':
cities.cpp:33:20: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
33 | for(int i = 0; i < sub.size(); i++) {
| ~~^~~~~~~~~~~~
cities.cpp:36:24: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<std::pair<long long int, long long int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
36 | for(int id = 0; id < V[u].size(); id++) {
| ~~~^~~~~~~~~~~~~
cities.cpp:34:8: warning: unused variable 'a' [-Wunused-variable]
34 | int a = sub[i];
| ^
cities.cpp:47:21: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<std::pair<long long int, long long int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
47 | for(int i = 0; i < V[u].size(); i++) {
| ~~^~~~~~~~~~~~~