train.cpp: In function 'bool dfs(int)':
train.cpp:13:18: warning: suggest parentheses around assignment used as truth value [-Wparentheses]
13 | return res[u]=1;
train.cpp:16:18: warning: suggest parentheses around assignment used as truth value [-Wparentheses]
16 | return res[u]=0;
train.cpp:22:16: warning: suggest parentheses around assignment used as truth value [-Wparentheses]
22 | return res[u]=ans;
train.cpp: In function 'std::vector<int> who_wins(std::vector<int>, std::vector<int>, std::vector<int>, std::vector<int>)':
train.cpp:26:16: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
26 | for(int i=0;i<a.size();i++){
| ~^~~~~~~~~
train.cpp:32:16: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
32 | for(int i=0;i<u.size();i++){
| ~^~~~~~~~~