marriage.cpp: In function 'bool try_dfs(int)':
marriage.cpp:14:19: 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 < V[u].size(); i++) {
| ~~^~~~~~~~~~~~~
marriage.cpp: At global scope:
marriage.cpp:34:1: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
34 | main(){
| ^~~~
marriage.cpp: In function 'int main()':
marriage.cpp:48:21: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
48 | for(int i = 0; i < x[r].size(); i++) V[r].push_back(x[r][i]), V[x[r][i]].push_back(r);
| ~~^~~~~~~~~~~~~