Compilare: user.cpp: In function ‘int main()’: user.cpp:43:34: 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:44:36: 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); ^ In file included from /usr/include/string.h:642:0, from /usr/include/c++/4.8/cstring:42, from /usr/include/i386-linux-gnu/c++/4.8/bits/stdc++.h:48, from user.cpp:1: In function ‘void* memset(void*, int, size_t)’, inlined from ‘int main()’ at user.cpp:46:33: /usr/include/i386-linux-gnu/bits/string3.h:82:32: warning: call to ‘__warn_memset_zero_len’ declared with attribute warning: memset used with constant zero length parameter; this could be due to transposed parameters [enabled by default] __warn_memset_zero_len (); ^ /tmp/ccf8wtSp.o: In function `main': user.cpp:(.text.startup+0x7c): warning: memset used with constant zero length parameter; this could be due to transposed parameters