Compilare: user.cpp: In function ‘void dfs2(int)’: user.cpp:57:23: warning: unused variable ‘mid’ [-Wunused-variable] int st,dr,mid,sol; ^ user.cpp: In function ‘void bfs()’: user.cpp:109:23: warning: unused variable ‘mid’ [-Wunused-variable] int st,dr,mid,sol; ^ user.cpp: In function ‘int main()’: user.cpp:143:39: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("harbingers.in","r",stdin); ^ user.cpp:144:41: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("harbingers.out","w",stdout); ^ user.cpp:146:19: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d",&n); ^ user.cpp:150:33: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d%d",&u,&w,&d); ^ user.cpp:155:48: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%lld%lld",&prepare[i],&speed[i]); ^ user.cpp: In function ‘void bfs()’: user.cpp:13:39: warning: ‘sol’ may be used uninitialized in this function [-Wmaybe-uninitialized] return (1LL*line[i].first)*(1LL*x)+(1LL*line[i].second); ^ user.cpp:109:27: note: ‘sol’ was declared here int st,dr,mid,sol; ^