Compilare: user.cpp: In function ‘bool bfs()’: user.cpp:21:38: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < m[x].size(); ++i) { ^ user.cpp: In function ‘void update_flow()’: user.cpp:34:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<m[N].size();++i) { ^ user.cpp: In function ‘int main()’: user.cpp:61:36: 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:62:38: 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:63:24: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d",&N,&M); ^ user.cpp:65:33: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d%d",&x,&y,&z); ^