Question

我的哈希表类的构造函数出错了，这是一个'Entry'对象的向量（下面的类定义）。

HT::HT (  const unsigned& s )
{
    hTable = new Entry[s];
    pTable = new Entry*[s];
    psize = 0;
    hsize = TBL_SZ;
    for (unsigned int i = 0; i != s; i++)
    {
        hTable[i].key = FREE;
    }
}

为什么我收到此错误？

    hTable.cc:12:15: error: expected type-specifier before âhTableâ
hTable.cc:12:15: error: no match for âoperator=â in â((HT*)this)->HT::hTable = (int*)operator new(4u)â
hTable.cc:12:15: note: candidate is:
/usr/include/c++/4.6/bits/vector.tcc:158:5: note: std::vector<_Tp, _Alloc>& std::vector<_Tp, _Alloc>::operator=(const std::vector<_Tp, _Alloc>&) [with _Tp = Entry, _Alloc = std::allocator<Entry>]
/usr/include/c++/4.6/bits/vector.tcc:158:5: note:   no known conversion for argument 1 from âint*â to âconst std::vector<Entry>&â
hTable.cc:12:15: error: expected â;â before âhTableâ
hTable.cc:13:15: error: expected type-specifier before âpTableâ
hTable.cc:13:15: error: no match for âoperator=â in â((HT*)this)->HT::pTable = (int*)operator new(4u)â
hTable.cc:13:15: note: candidate is:
/usr/include/c++/4.6/bits/vector.tcc:158:5: note: std::vector<_Tp, _Alloc>& std::vector<_Tp, _Alloc>::operator=(const std::vector<_Tp, _Alloc>&) [with _Tp = Entry*, _Alloc = std::allocator<Entry*>]
/usr/include/c++/4.6/bits/vector.tcc:158:5: note:   no known conversion for argument 1 from âint*â to âconst std::vector<Entry*>&â

这是头文件：

    #ifndef H_HASH_TABLE
#define H_HASH_TABLE

// class for hash table

class HT {
public:
    HT ( const unsigned& = TBL_SZ ); // constructor
    ~HT ( );                         // destructor

    void insert ( const Entry& );    // inserts item in hash table
    void search ( const string& );   // searches for item

    void hTable_print ( ); // prints hash table entries
    void pTable_print ( ); // prints hash table entries in sorted order

private:
    unsigned hsize,             // size of hash table
             psize;             // actual size of ptr table

    vector < Entry >  hTable;   // hash table
    vector < Entry* > pTable;   // ptr table

    int hash ( const string& ); // hash function
};
#endif

这是我的Entry对象标题：

#ifndef H_ENTRY
#define H_ENTRY

#define ID_SZ    3      // size of key
#define ITEM_SZ 24      // max size for item description 
#define TBL_SZ  31      // default size for hash table
#define FREE   "$$$"    // indicates empty spot in hash table

// entry in hash table

struct Entry {
    string key;   // key
    string desc;  // description
    unsigned num; // no of copies

    //constructor
    Entry ( const string& k = FREE, const string& d = "",
        const unsigned& n = 0 ) : key ( k ), desc ( d ),
        num ( n ) { }
};
#endif

Answer 1

成员的声明

vector < Entry >  hTable;   // hash table
vector < Entry* > pTable;   // ptr table

与初始化完全匹配

hTable = new Entry[s];
pTable = new Entry*[s];

std::vector不是指针，不应使用new创建。它们由vector构造函数自动初始化。

如果要设置向量的大小，可以在构造函数初始化列表中执行此操作，或者通过调整默认构造向量的大小：

HT::HT (  const unsigned& s )
{
    hTable.resize(s);
    pTable.resize(s);
    psize = 0;
    hsize = TBL_SZ;
    for (unsigned int i = 0; i != s; i++)
    {
        hTable[i].key = FREE;
    }
}

Answer 2

new Entry[s];创建一个Entry对象数组，并尝试将其分配给向量。新的Entry * [s]也是如此。您需要确定hTable和pTables是否需要是向量或用

替换它

Entry *hTable Entry **pTable。

哈希表构造函数出错

2 个答案: