Compilare: user.cpp: In function ‘int breadthfirst()’: user.cpp:33:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(j=0; j<arcs[curr_node].size(); ++j) ~^~~~~~~~~~~~~~~~~~~~~~~ user.cpp: In function ‘int main()’: user.cpp:67:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0; i<arcs[n].size(); ++i) ~^~~~~~~~~~~~~~~ user.cpp:51:38: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("maxflow.in", "r", stdin); ^ user.cpp:52:40: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("maxflow.out", "w", stdout); ^ user.cpp:55:26: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d", &n, &m); ^ user.cpp:59:36: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d%d", &x, &y, &j); ^