<span>哈希表实现</span>

1 //映射方法，BKDRHash方法
2 static int32_t BKDRHash(const string& str){
3     int32_t hash=0,seed = 131;
4     for(uint32_t i=0;i<str.length();i++){
5         hash = hash * seed + str[i];
6     }
7     return (hash & 0x7fffffff);
8 }

  1 /***************************************
  2 FileName ：HashTable.cpp
  3 Author : godfrey
  4 CreatedTime : 2016/5/1
  5 ****************************************/
  6 #include <iostream>
  7 #include <cstring>
  8 #include <stdio.h>
  9 #include <stdlib.h>
 10 
 11 using namespace std;
 12 
 13 class hash_node{
 14 public:
 15     hash_node() {
 16         this->data = "";
 17         this->next = NULL;
 18     }
 19     ~hash_node() {}
 20     void SetData(string data){
 21         this->data = data;
 22     }
 23     string GetData(){
 24         return this->data;
 25     }
 26     void SetNext(hash_node* next){
 27         this->next = next;
 28     }
 29     hash_node* GetNext(){
 30         return this->next;
 31     }
 32 private:
 33     string data;
 34     hash_node* next;
 35 };
 36 
 37 class hash_table{
 38 public:
 39     hash_table(int32_t hash_table_len,int32_t node_pool_len){
 40         this->hash_table_len = hash_table_len;
 41         this->node_pool_len = node_pool_len;
 42         this->node_pool_cnt = 0;
 43         try{
 44             this->hash_table_main = new hash_node*[this->hash_table_len];
 45             memset(this->hash_table_main,0,sizeof(hash_node*)*(this->hash_table_len));
 46             this->hash_node_pool = new hash_node[this->node_pool_len];
 47         }catch(const bad_alloc & e){
 48             std::cerr<<"there is no more place"<<endl;
 49         }
 50     }
 51     ~hash_table(){
 52         delete[] this->hash_table_main;
 53         delete[] this->hash_node_pool;
 54     }
 55     //哈希表的插入操作，使用拉链法
 56     bool insert(string str,bool& Is_uniqe){
 57         if(true == this->search(str)){
 58             Is_uniqe = false;
 59             return true;
 60         }
 61         //拉链法插入
 62         hash_node* p;
 63         hash_node* q = this->GetNewNode();
 64         if(q == NULL) return false;
 65         int32_t index = this->GetHashIndex(str);
 66         p = this->hash_table_main[index];
 67         q->SetData(str);
 68         q->SetNext(p);
 69         this->hash_table_main[index] = q;
 70         Is_uniqe = true;
 71         return true;
 72     }
 73     //哈希表的查找操作
 74     bool search(string str){
 75         int32_t index = this->GetHashIndex(str);
 76         hash_node* p = this->hash_table_main[index];
 77         while(p){
 78             if(p->GetData()==str) return true;
 79             p = p->GetNext();
 80         }
 81         return false;
 82     }
 83 private:
 84     hash_node** hash_table_main;//哈希表的大小
 85     hash_node* hash_node_pool;//哈希表的内存池
 86 
 87     int32_t hash_table_len,node_pool_len,node_pool_cnt;
 88     //映射方法，BKDRHash方法
 89     static int32_t BKDRHash(const string& str){
 90         int32_t hash=0,seed = 131;
 91         for(uint32_t i=0;i<str.length();i++){
 92             hash = hash * seed + str[i];
 93         }
 94         return (hash & 0x7fffffff);
 95     }
 96     //获取哈希表中字符串相应的索引
 97     int32_t GetHashIndex(string& str){
 98         if(hash_table_len == 0) return 0;
 99         return (hash_table::BKDRHash(str)%this->hash_table_len);
100     }
101     //在内存池中获取新的节点内存
102     hash_node* GetNewNode(){
103         if(this->node_pool_cnt>=this->node_pool_len) return NULL;
104         return &this->hash_node_pool[node_pool_cnt++];
105     }
106 };
107 
108 int main()
109 {
110     hash_table ht(100,1000);
111     bool is_uniqe,flag;
112     ht.insert("godfrey",is_uniqe);
113     cout<<"ht.insert godfrey : "<<is_uniqe<<endl;
114     ht.insert("good",is_uniqe);
115     cout<<"ht.insert good : "<<is_uniqe<<endl;
116     ht.insert("godfrey",is_uniqe);
117     cout<<"ht.insert godfrey twice : "<<is_uniqe<<endl;
118     flag = ht.search("godfrey");
119     cout<<"ht.search godfrey : "<<flag<<endl;
120     return 0;
121 }