C ++如何插入数组哈希集合？ [英] C++ how to insert array into hash set?

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问题描述

我需要插入一维数组到HashSet的。

不过，在编译时我得到了错误。

 的#include＆LT;＆stdio.h中GT;
＃包括LT＆;＆stdlib.h中GT;
＃包括LT＆;＆hash_set.h GT;
使用命名空间std;
INT hash_comp（const int的* STATE1，const int的* STATE2）{
    INT结果为0;    对于（i = 0; I＆LT; 16;我++）
    {
        如果（STATE1 [I]！= STATE2 [I]）{
            结果= -1;
        }    }
    返回结果;
}
结构eqArray
{
    布尔运算符（）（const int的* A1，const int的* A2）常量
  {
    返回hash_comp（A1，A2）== 0;
  }
};
的hash_set＆LT; INT *，散列＆LT; INT *＆GT;，＆eqArray GT; closelist;
INT主（INT ARGC，字符** argv的）
{
   const int的SN [16] = {1,2,3,4,5,6,0,8,9,10,11,12,13,14,7,15};
   closelist.insert（SN）;
   返回0;
}
 

  / usr / include目录/ C ++ / 4.2.1 /转/ hashtable.h：在成员函数'为size_t __gnu_cxx ::哈希表＆LT; _Val，_key，_HashFcn，_ExtractKey，_EqualKey，_Alloc＆GT ; :: _ M_bkt_num_key（常量_key＆安培;，为size_t）常量[与_Val = INT *，_key = INT *，_HashFcn = __gnu_cxx ::散列＆LT; INT *＆gt;中_ExtractKey =的std :: _身份＆LT; INT *＆gt;中_EqualKey =的std :: equal_to＆LT; INT *＆gt;中_Alloc =的std ::分配器＆LT; INT *＆GT;]'：
/usr/include/c++/4.2.1/ext/hashtable.h:599：从'为size_t __gnu_cxx ::哈希表＆LT实例; _Val，_key，_HashFcn，_ExtractKey，_EqualKey，_Alloc＆GT; :: _ M_bkt_num（常量_Val＆安培;，为size_t）常量[与_Val = INT *，_key = INT *，_HashFcn = __gnu_cxx ::散列＆LT; INT *＆gt;中_ExtractKey =的std :: _身份＆LT; INT *＆gt;中_EqualKey =的std :: equal_to＆LT; INT *＆gt;中_Alloc =的std ::分配器＆LT; INT *＆GT;]
/usr/include/c++/4.2.1/ext/hashtable.h:1006：从'无效__gnu_cxx ::哈希表＆LT实例; _Val，_key，_HashFcn，_ExtractKey，_EqualKey，_Alloc＆GT; ::调整（为size_t）与_Val =为int *，_key = INT *，_HashFcn = __gnu_cxx ::散列＆LT; INT *＆gt;中_ExtractKey =的std :: _身份＆LT; INT *＆gt;中_EqualKey =的std :: equal_to＆LT; INT *＆gt;中_Alloc =的std ::分配器＆LT ;为int *＆GT;]
/usr/include/c++/4.2.1/ext/hashtable.h:437：从'的std ::对实例化＆LT; __ gnu_cxx :: _ Hashtable_iterator＆LT; _Val，_key，_HashFcn，_ExtractKey，_EqualKey，_Alloc＆gt;中布尔＆GT; __gnu_cxx ::哈希表＆LT; _Val，_key，_HashFcn，_ExtractKey，_EqualKey，_Alloc＆GT; :: insert_unique（常量_Val＆安培;）与_Val = INT *，_key = INT *，_HashFcn = __gnu_cxx ::散列＆LT; INT *＆gt;中_ExtractKey =的std :: _身份＆LT; INT *＆gt;中_EqualKey =的std :: equal_to＆LT; INT *＆gt;中_Alloc =的std ::分配器＆LT; INT *＆GT;]
/usr/include/c++/4.2.1/ext/hash_set:197：从'的std ::对＆LT实例化，类型名__gnu_cxx ::哈希表＆LT; _Value，_Value，_HashFcn，性病:: _身份＆LT; _TP＆gt;中_EqualKey，_Alloc计算值： ：常量性，布尔＆GT; __gnu_cxx ::的hash_set＆LT; _Value，_HashFcn，_EqualKey，_Alloc＆GT; ::插入（常量类型名称__gnu_cxx ::哈希表＆LT; _Value，_Value，_HashFcn，性病:: _身份＆LT; _TP＆gt;中_EqualKey，_Alloc＆GT; :: VALUE_TYPE＆安培;）与_Value = INT *，_HashFcn = __gnu_cxx ::散列＆LT; INT *＆gt;中_EqualKey =的std :: equal_to＆LT; INT *＆gt;中_Alloc =的std ::分配器＆LT; INT *＆GT;]
SRC / ods2.cpp：677：从这里实例化


解决方案

如果您使用的是的std ::阵列＆LT; INT，16＆GT; 而不是为int * ，所有的问题就会迎刃而解。如果你没有C ++编译器11，可以使用的boost ::阵列来代替。此外，替换的hash_set 与 unordered_set 。

这似乎没有的std ::哈希为的std ::阵列取值专业化，所以我写了我自己的：

 的#include＆LT; unordered_set＆GT;
＃包括LT＆;阵列GT;空间std
{
    模板＆LT; typename的T，为size_t N'GT;
    结构散列＆LT;阵列LT; T，N＆GT; ＆GT;
    {
        typedef的数组＆LT; T，N＆GT; argument_type;
        的typedef result_type的为size_t;        result_type的运算符（）（常量argument_type＆放大器;一）常量
        {
            哈希＆LT; T＆GT;散列器;
            result_type的H = 0;
            对于（result_type的I = 0; I＆LT; N ++ I）
            {
                H = H * 31 +散列器（A []​​）;
            }
            返回H;
        }
    };
}的std :: unordered_set＆LT;的std ::阵列＆LT; INT，16取代; ＆GT; closelist;诠释的main（）
{
    的std ::阵列＆LT; INT，16取代; SN = {} 1,2,3,4,5,6,0,8,9,10,11,12,13,14,7,15;
    closelist.insert（SN）;
}

I need to insert a 1D array into the hashset.

But I got error while compiling.

#include <stdio.h>
#include <stdlib.h>
#include <hash_set.h>
using namespace std;
int hash_comp(const int* state1,const int* state2) {
    int result = 0;

    for (i = 0; i < 16; i++) 
    {
        if (state1[i] != state2[i]) {
            result = -1;
        }

    }
    return result;
}
struct eqArray
{
    bool operator()(const int* a1,const int* a2) const
  {
    return hash_comp(a1,a2) == 0;
  }
};
hash_set<int*,hash<int*>,eqArray> closelist;
int main(int argc, char** argv)
{
   const int sn[16] = {1,2,3,4,5,6,0,8,9,10,11,12,13,14,7,15};
   closelist.insert(sn);
   return 0;
}


/usr/include/c++/4.2.1/ext/hashtable.h: In member function 'size_t __gnu_cxx::hashtable<_Val, _Key, _HashFcn, _ExtractKey, _EqualKey, _Alloc>::_M_bkt_num_key(const _Key&, size_t) const [with _Val = int*, _Key = int*, _HashFcn = __gnu_cxx::hash<int*>, _ExtractKey = std::_Identity<int*>, _EqualKey = std::equal_to<int*>, _Alloc = std::allocator<int*>]':
/usr/include/c++/4.2.1/ext/hashtable.h:599:   instantiated from 'size_t __gnu_cxx::hashtable<_Val, _Key, _HashFcn, _ExtractKey, _EqualKey, _Alloc>::_M_bkt_num(const _Val&, size_t) const [with _Val = int*, _Key = int*, _HashFcn = __gnu_cxx::hash<int*>, _ExtractKey = std::_Identity<int*>, _EqualKey = std::equal_to<int*>, _Alloc = std::allocator<int*>]'
/usr/include/c++/4.2.1/ext/hashtable.h:1006:   instantiated from 'void __gnu_cxx::hashtable<_Val, _Key, _HashFcn, _ExtractKey, _EqualKey, _Alloc>::resize(size_t) [with _Val = int*, _Key = int*, _HashFcn = __gnu_cxx::hash<int*>, _ExtractKey = std::_Identity<int*>, _EqualKey = std::equal_to<int*>, _Alloc = std::allocator<int*>]'
/usr/include/c++/4.2.1/ext/hashtable.h:437:   instantiated from 'std::pair<__gnu_cxx::_Hashtable_iterator<_Val, _Key, _HashFcn, _ExtractKey, _EqualKey, _Alloc>, bool> __gnu_cxx::hashtable<_Val, _Key, _HashFcn, _ExtractKey, _EqualKey, _Alloc>::insert_unique(const _Val&) [with _Val = int*, _Key = int*, _HashFcn = __gnu_cxx::hash<int*>, _ExtractKey = std::_Identity<int*>, _EqualKey = std::equal_to<int*>, _Alloc = std::allocator<int*>]'
/usr/include/c++/4.2.1/ext/hash_set:197:   instantiated from 'std::pair<typename __gnu_cxx::hashtable<_Value, _Value, _HashFcn, std::_Identity<_Tp>, _EqualKey, _Alloc>::const_iterator, bool> __gnu_cxx::hash_set<_Value, _HashFcn, _EqualKey, _Alloc>::insert(const typename __gnu_cxx::hashtable<_Value, _Value, _HashFcn, std::_Identity<_Tp>, _EqualKey, _Alloc>::value_type&) [with _Value = int*, _HashFcn = __gnu_cxx::hash<int*>, _EqualKey = std::equal_to<int*>, _Alloc = std::allocator<int*>]'
src/ods2.cpp:677:   instantiated from here

解决方案

If you use a std::array<int, 16> instead of int*, all your problems will go away. If you have no C++11 compiler, you can use boost::array instead. Also, replace hash_set with unordered_set.

It appears there is no specialization of std::hash for std::arrays, so I wrote my own:

#include <unordered_set>
#include <array>

namespace std
{
    template<typename T, size_t N>
    struct hash<array<T, N> >
    {
        typedef array<T, N> argument_type;
        typedef size_t result_type;

        result_type operator()(const argument_type& a) const
        {
            hash<T> hasher;
            result_type h = 0;
            for (result_type i = 0; i < N; ++i)
            {
                h = h * 31 + hasher(a[i]);
            }
            return h;
        }
    };
}

std::unordered_set<std::array<int, 16> > closelist;

int main()
{
    std::array<int, 16> sn = {1,2,3,4,5,6,0,8,9,10,11,12,13,14,7,15};
    closelist.insert(sn);
}

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