<span>哈希表实现</span>
哈希表实现:
使用BKDRHash作为基础的哈希函数,同时使用拉链法作为冲突处理方法,实现哈希表的插入和查找操作。
哈希函数BKDRHash实现如下:
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 }
处理冲突的方法有拉链法,开放定址和再哈希法。各种冲突方法如何实现,可以自行查资料进行学习,这里不做详细介绍。另附一张图,说明拉链法(说明版权:来源小象学院huge的算法讲解PPT)。
程序实现:
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 }
运行结果:
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C++博客园:godfrey_88
http://www.cnblogs.com/gaobaoru-articles/