Compilare: user.cpp: In function ‘void DFS2(int, int)’: user.cpp:37:42: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i = 0; i < G[1].size()&&ok; ++i) ^ user.cpp:44:42: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i = 0; i < G[1].size()&&ok; ++i) ^ user.cpp:51:42: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i = 0; i < G[1].size()&&ok; ++i) ^ user.cpp: In function ‘int main()’: user.cpp:62:36: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen ("arbxyz.in","r",stdin); ^ user.cpp:63:38: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen ("arbxyz.out","w",stdout); ^ user.cpp:65:21: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d\n",&t); ^ user.cpp:68:43: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d %d %d\n",&N,&x,&y,&z); ^ user.cpp:75:35: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d\n",&a,&b); ^