train.cpp: In function 'std::vector<int> who_wins(std::vector<int>, std::vector<int>, std::vector<int>, std::vector<int>)':
train.cpp:15:23: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
15 | for (int i = 0; i < a.size(); i++)
| ~~^~~~~~~~~~
train.cpp:17:23: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
17 | for (int i = 0; i < u.size(); i++) {
| ~~^~~~~~~~~~
train.cpp:29:23: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
29 | for (int i = 0; i < a.size(); i++) {
| ~~^~~~~~~~~~
train.cpp:36:21: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
36 | if (nw < nl && nw <= nl2 || (nl > nl2 && r[nl2]))
| ~~~~~~~~^~~~~~~~~~~~