我需要C++(STL)中的hash_map类。主要操作是将对放入集合中,然后检查它是否存在。如何在STL中使用unordered_set?
我无法找到一个示例代码,它知道我是否正确地声明了它。
#include <iostream>
#include <hash_map>
using namespace std;
using namespace __gnu_cxx;
typedef pair<int,string> pis;
struct eqpis {
bool operator()(pis p1,pis p2) const {
if(p1==p2) return true;
return false;
}
};
int main() {
hash_map<pis,int,hash<pis>,eqpis> map;
}
这个编译。但如果我添加该行: map [pis(10,“hello”)] = 10; 那么它给了很多的错误:
/usr/include/c++/4.4/backward/hashtable.h: In member function ‘size_t __gnu_cxx::hashtable::_M_bkt_num_key(const _Key&, size_t) const [with _Val = std::pair, std::allocator > >, int>, _Key = std::pair, std::allocator > >, _HashFcn = __gnu_cxx::hash, std::allocator > > >, _ExtractKey = std::_Select1st, std::allocator > >, int> >, _EqualKey = eqpis, _Alloc = std::allocator]’: /usr/include/c++/4.4/backward/hashtable.h:594: instantiated from ‘size_t __gnu_cxx::hashtable::_M_bkt_num(const _Val&, size_t) const [with _Val = std::pair, std::allocator > >, int>, _Key = std::pair, std::allocator > >, _HashFcn = __gnu_cxx::hash, std::allocator > > >, _ExtractKey = std::_Select1st, std::allocator > >, int> >, _EqualKey = eqpis, _Alloc = std::allocator]’ /usr/include/c++/4.4/backward/hashtable.h:1001: instantiated from ‘void __gnu_cxx::hashtable::resize(size_t) [with _Val = std::pair, std::allocator > >, int>, _Key = std::pair, std::allocator > >, _HashFcn = __gnu_cxx::hash, std::allocator > > >, _ExtractKey = std::_Select1st, std::allocator > >, int> >, _EqualKey = eqpis, _Alloc = std::allocator]’ /usr/include/c++/4.4/backward/hashtable.h:789: instantiated from ‘_Val& __gnu_cxx::hashtable::find_or_insert(const _Val&) [with _Val = std::pair, std::allocator > >, int>, _Key = std::pair, std::allocator > >, _HashFcn = __gnu_cxx::hash, std::allocator > > >, _ExtractKey = std::_Select1st, std::allocator > >, int> >, _EqualKey = eqpis, _Alloc = std::allocator]’ /usr/include/c++/4.4/backward/hash_map:216: instantiated from ‘_Tp& __gnu_cxx::hash_map::operator[](const typename __gnu_cxx::hashtable, _Key, _HashFn, std::_Select1st >, _EqualKey, _Alloc>::key_type&) [with _Key = std::pair, std::allocator > >, _Tp = int, _HashFn = __gnu_cxx::hash, std::allocator > > >, _EqualKey = eqpis, _Alloc = std::allocator]’ x.cpp:18: instantiated from here /usr/include/c++/4.4/backward/hashtable.h:590: error: no match for call to ‘(const __gnu_cxx::hash, std::allocator > > >) (const std::pair, std::allocator > >&)’
感谢