HashTable的C++实现

由哈希表的定义，采用C++完成了一个学生成绩存储系统，分析过程如下：

由于哈希表是按KEY值存储，我们假设KEY值为一个字符串。hash算法为字符串的前两位大写字母所对应的数字对一个质数的模运算。

int Hash(KeyType c)
{
    int n = c[0] - 'A'+c[1]-'A'+2;
    return n % Mod;
}

哈希表的类定义如下

class HashTable
{
public:
//    HashTable();
    HashTable(int len);
    ~HashTable();
    bool SearchHash(KeyType K, int &p, int &c,int &s);
    bool InsertHash(ElemType e);
private:
    ElemType * elem;
    int count;
    int sizeindex;
};

搜索函数SearchHash

bool HashTable::SearchHash(KeyType K, int &p, int &c,int &s)
{
    c = 0;
    p = Hash(K);
    std::string NULLKey = "None";
    while (this->elem[p].key != NULLKey && K != this->elem[p].key)
    {
        p++;
        c++;//冲突次数++
    }
//    cout << "after,p = " << p << endl;
    if (K == this->elem[p].key)
    {
        s = elem[p].score;
        return true;
    }
    else
        return false;
}

插入函数InsertHash

bool HashTable::InsertHash(ElemType e)
{
    int c = 0;//c为冲突次数
    int p,s;
    if (SearchHash(e.key, p, c,s))
        return false;
    else if (c < Hashsize[this->sizeindex] / 2)
    {
        this->elem[p] = e;
        this->count++;
        return true;
    }
    else
    {
        HashTable();
        return false;
    }
}

任务源代码如下：

哈希表元素类

//ElemType.h

#ifndef ELEMTYPE_H
#define ELEMTYPE_H
#include<string>
typedef std::string KeyType;
class ElemType
{
public:
    KeyType key;
    int score;
};
#endif

哈希表类

//HashTable.h

#ifndef HASHTABLE_H
#define HASHTABLE_H
#include"ElemType.h"

class HashTable
{
public:
//    HashTable();
    HashTable(int len);
    ~HashTable();
    bool SearchHash(KeyType K, int &p, int &c,int &s);
    bool InsertHash(ElemType e);
private:
    ElemType * elem;
    int count;
    int sizeindex;
};


#endif

哈希表的操作函数

//HashTable.cpp

#include"HashTable.h"
#include<iostream>
using namespace std;
const int Mod = 19;//质数模
int Hashsize[] = { 47,71,97,133 };
int Hash(KeyType c)
{
    int n = c[0] - 'A'+c[1]-'A'+2;
    return n % Mod;
}

HashTable::HashTable(int len=20)
{
    elem = new ElemType[len];
    for (int i = 0; i < len; i++)
    {
        elem[i].key = "None";
    }
    count = 0;
    sizeindex = 0;
}

HashTable::~HashTable()
{
    delete[] elem;
    count = 0;
    sizeindex = 0;
}

bool HashTable::SearchHash(KeyType K, int &p, int &c,int &s)
{
    c = 0;
    p = Hash(K);
    std::string NULLKey = "None";
    while (this->elem[p].key != NULLKey && K != this->elem[p].key)
    {
        p++;
        c++;//冲突次数++
    }
//    cout << "after,p = " << p << endl;
    if (K == this->elem[p].key)
    {
        s = elem[p].score;
        return true;
    }
    else
        return false;
}

bool HashTable::InsertHash(ElemType e)
{
    int c = 0;//c为冲突次数
    int p,s;
    if (SearchHash(e.key, p, c,s))
        return false;
    else if (c < Hashsize[this->sizeindex] / 2)
    {
        this->elem[p] = e;
        this->count++;
        return true;
    }
    else
    {
        HashTable();
        return false;
    }
}

信息存储的实现

//Main.cpp

#include"HashTable.h"
#include<iostream>
using namespace std;
int main()
{
    HashTable* H = new HashTable(100);
    ElemType e;
    int p,c;
    int i=1;
    KeyType k;
    int score;
    while (i != 0)
    {
        switch (i)
        {
        case 1:
            cout << "***______HashTable_____***" << endl;
            cout << "***___1.Display menu___***" << endl;
            cout << "***___2.Insert_________***" << endl;
            cout << "***___3.Search_________***" << endl;
            cout << "***___0.Exit___________***" << endl;
            break;
        case 2:
            cout << "input name with A~Z: ";
            cin >> k;
            e.key = k;
            cout << "input score with number: ";
            cin >> score;
            e.score = score;
            H->InsertHash(e);
            break;
        case 3:
            cout << "input name with A~Z: ";
            cin >> k;
            if (H->SearchHash(k, p, c, score))
            {
                cout << k << "'s score is " << score << endl;;
            }
            else
                cout << "can't found" << endl;
            break;

        }
        cout << "输入选项：";
        cin >> i;
    }
    system("pause");
    return 0;
}

效果如下

***______HashTable_____***
***___1.Display menu___***
***___2.Insert_________***
***___3.Search_________***
***___0.Exit___________***
输入选项：2
input name with A~Z: DSG
input score with number: 99
输入选项：2
input name with A~Z: QWER
input score with number: 70
输入选项：3
input name with A~Z: DSG
DSG's score is 99
输入选项：2
input name with A~Z: OOP
input score with number: 100
输入选项：3
input name with A~Z: QWER
QWER's score is 70
输入选项：3
input name with A~Z: OOP
OOP's score is 100
输入选项：0
请按任意键继续. . .