Compilare: user.cpp: In function ‘void buildGraph()’: user.cpp:24:40: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(j=0; j<edges[v[i].to].size(); ++j) { ^ user.cpp: In function ‘int main()’: user.cpp:41:37: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("tester.in", "r", stdin); ^ user.cpp:42:39: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("tester.out", "w", stdout); ^ user.cpp:46:26: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d", &n, &m); ^ user.cpp:48:44: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d", &v[i].from, &v[i].to); ^