Compilare: user.cpp: In function ‘void dfs(graph*&, int, std::stack<int>&, bool*)’: user.cpp:55:49: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < graf->lists[source].size(); i++) { ^ user.cpp: In function ‘int main()’: user.cpp:105:15: warning: unused variable ‘S’ [-Wunused-variable] int N, M, S, i, u, v; ^ user.cpp:103:37: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("gcycle.in", "r", stdin); ^ user.cpp:104:39: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("gcycle.out", "w", stdout); ^ user.cpp:106:27: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d", &N, &M); ^ user.cpp:109:31: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d", &u, &v); ^