Compilare: user.cpp: In function ‘void DFS(int)’: user.cpp:11:25: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(k=0;k<f[x].size();k++) ^ user.cpp:10:11: warning: unused variable ‘i’ [-Wunused-variable] int k,i,m; ^ user.cpp:10:13: warning: unused variable ‘m’ [-Wunused-variable] int k,i,m; ^ user.cpp: In function ‘int main()’: user.cpp:22:32: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("dfs.in","r",stdin); ^ user.cpp:23:34: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("dfs.out","w",stdout); ^ user.cpp:24:24: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d",&x,&m); ^ user.cpp:27:28: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d",&i,&j); ^