Eroare de compilare: user.cpp: In function ‘void bellman_ford(int)’: user.cpp:30:38: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < a[k].size(); ++i) ^ In file included from /usr/include/c++/4.8/bits/hashtable.h:35:0, from /usr/include/c++/4.8/unordered_map:47, from user.cpp:6: /usr/include/c++/4.8/bits/hashtable_policy.h: In instantiation of ‘struct std::__detail::_Hash_code_base<std::pair<int, int>, std::pair<const std::pair<int, int>, int>, std::__detail::_Select1st, std::hash<std::pair<int, int> >, std::__detail::_Mod_range_hashing, std::__detail::_Default_ranged_hash, true>’: /usr/include/c++/4.8/bits/hashtable_policy.h:1402:10: required from ‘struct std::__detail::_Hashtable_base<std::pair<int, int>, std::pair<const std::pair<int, int>, int>, std::__detail::_Select1st, std::equal_to<std::pair<int, int> >, std::hash<std::pair<int, int> >, std::__detail::_Mod_range_hashing, std::__detail::_Default_ranged_hash, std::__detail::_Hashtable_traits<true, false, true> >’ /usr/include/c++/4.8/bits/hashtable.h:174:11: required from ‘class std::_Hashtable<std::pair<int, int>, std::pair<const std::pair<int, int>, int>, std::allocator<std::pair<const std::pair<int, int>, int> >, std::__detail::_Select1st, std::equal_to<std::pair<int, int> >, std::hash<std::pair<int, int> >, std::__detail::_Mod_range_hashing, std::__detail::_Default_ranged_hash, std::__detail::_Prime_rehash_policy, std::__detail::_Hashtable_traits<true, false, true> >’ /usr/include/c++/4.8/bits/unordered_map.h:100:18: required from ‘class std::unordered_map<std::pair<int, int>, int>’ user.cpp:47:36: required from here /usr/include/c++/4.8/bits/hashtable_policy.h:1070:12: error: invalid use of incomplete type ‘struct std::hash<std::pair<int, int> >’ struct _Hash_code_base<_Key, _Value, _ExtractKey, _H1, _H2, ^ In file included from /usr/include/c++/4.8/bits/basic_string.h:3033:0, from /usr/include/c++/4.8/string:52, from /usr/include/c++/4.8/bits/locale_classes.h:40, from /usr/include/c++/4.8/bits/ios_base.h:41, from /usr/include/c++/4.8/ios:42, from /usr/include/c++/4.8/istream:38, from /usr/include/c++/4.8/fstream:38, from user.cpp:1: /usr/include/c++/4.8/bits/functional_hash.h:58:12: error: declaration of ‘struct std::hash<std::pair<int, int> >’ struct hash; ^ In file included from /usr/include/c++/4.8/bits/hashtable.h:35:0, from /usr/include/c++/4.8/unordered_map:47, from user.cpp:6: /usr/include/c++/4.8/bits/hashtable_policy.h:1070:12: error: invalid use of incomplete type ‘struct std::hash<std::pair<int, int> >’ struct _Hash_code_base<_Key, _Value, _ExtractKey, _H1, _H2, ^ In file included from /usr/include/c++/4.8/bits/basic_string.h:3033:0, from /usr/include/c++/4.8/string:52, from /usr/include/c++/4.8/bits/locale_classes.h:40, from /usr/include/c++/4.8/bits/ios_base.h:41, from /usr/include/c++/4.8/ios:42, from /usr/include/c++/4.8/istream:38, from /usr/include/c++/4.8/fstream:38, from user.cpp:1: /usr/include/c++/4.8/bits/functional_hash.h:58:12: error: declaration of ‘struct std::hash<std::pair<int, int> >’ struct hash; ^ In file included from /usr/include/c++/4.8/bits/hashtable.h:35:0, from /usr/include/c++/4.8/unordered_map:47, from user.cpp:6: /usr/include/c++/4.8/bits/hashtable_policy.h:1082:53: error: invalid use of incomplete type ‘struct std::hash<std::pair<int, int> >’ using __ebo_h1 = _Hashtable_ebo_helper<1, _H1>; ^ In file included from /usr/include/c++/4.8/bits/basic_string.h:3033:0,