Compilare: user.cpp: In function ‘void DFS(int)’: user.cpp:17:14: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0;i< matrice[a].size();++i) ~^~~~~~~~~~~~~~~~~~~ user.cpp: In function ‘int main()’: user.cpp:30:9: warning: unused variable ‘a’ [-Wunused-variable] int a = 0; ^ user.cpp:27:32: 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:28:34: 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:29:27: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d\n",&n, &m); ^ user.cpp:33:30: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d\n",&x,&y); ^