哈希函数编程实现

#include<cstdio>#include<iostream>#include<cstring>#include<cstdlib>#include<fstream>#include<ctime>using namespace std;class Hash;class Node{//边节点类public:Node(char *ptr){int len=strlen(ptr);str=new char[len+1];for(int i=0;i<len;i++){str[i]=ptr[i];}str[len]='\0';next=NULL;}~Node(){delete []str;}friend class Hash;//定义为友元private:char* str;Node*next;};class Hash{//哈希散列表类public:Hash(int len=0){//构造函数length=len;count=0;head=new Node*[len];for(int i=0;i<length;i++){head[i]=NULL;}file=NULL;}~Hash(){//析构函数ClearList();//用于清空哈希表中的数据delete[]head;}void HashTest(int type){//运用哈希函数进行测试，tupe=0为BKDR,type=1为ELF,type=2为AP,type=3为自己设计哈希函数ClearList();//用于清空散列表中的数据，进行新的哈希函数测试file=fopen("data.txt","r");//指定读入文件为data.txtif(file==NULL){cout<<"文件打开失败!"<<endl;return ;}char str[32];//假定每个字符长度不超过32unsigned int position;while(!feof(file)){count++;fscanf(file,"%s",str);if(type==0){position=BKDRHash(str);}else if(type==1){position=ELFHash(str);}else if(type==2){position=APHash(str);}else{position=MyHash(str);}position=position%length;Node *node=new Node(str);if(head[position]==NULL){head[position]=node;}else{Node*temp;temp=head[position];while(temp->next!=NULL){temp=temp->next;}temp->next=node;}}fclose(file);Assess(type);//计算桶使用率和平均桶长}void SetFile(int num){//设计随机数据文件ofstream fout("data.txt");if(!fout.is_open()){cout<<"无法打开输出流!!程序退出"<<endl;exit(0);}srand(time(0));//置随机数种子，一个随机数序列只需置一次。

for(int i=0;i<num;i++){int clength=1+rand()%32;//字符串的长度1到32,全字母字符串for(int j=0;j<clength;j++){int d=65+rand()%58;if(!('Z'<d&&d<'a')){char cname=(char)(d);fout<<cname;}else{j--;}}if(i!=num-1)fout<<" ";}fout.close();}void Display(){//查看哈希表内存存入状态Node*temp;for(int i=0;i<length;i++){temp=head[i];if(temp==NULL){cout<<i+1<<"."<<" "<<endl;}else{cout<<i+1<<".";while(temp!=NULL){cout<<temp->str<<" ";temp=temp->next;}cout<<endl;}}}private:void Assess(int type){//计算评价指标，输出到控制台int backet_num=0;for(int i=0;i<length;i++){if(head[i]!=NULL){backet_num++;}}backet_usage=(float)backet_num/length;avg_backet_len=(float)count/backet_num;if(type==0){cout<<"测试"<<count<<"数据"<<"BKDR哈希函数的指标:"<<endl;cout<<"桶的使用率为:"<<backet_usage*100<<"%"<<endl;cout<<"桶的平均长度为:"<<avg_backet_len*100<<"%"<<endl;}else if(type==1){cout<<"测试"<<count<<"数据"<<"ELF哈希函数的指标:"<<endl;cout<<"桶的使用率为:"<<backet_usage*100<<"%"<<endl;cout<<"桶的平均长度为:"<<avg_backet_len*100<<"%"<<endl;}else if(type==2){cout<<"测试"<<count<<"数据"<<"AP哈希函数的指标:"<<endl;cout<<"桶的使用率为:"<<backet_usage*100<<"%"<<endl;cout<<"桶的平均长度为:"<<avg_backet_len*100<<"%"<<endl;}else{cout<<"测试"<<count<<"数据"<<"My哈希函数的指标:"<<endl;cout<<"桶的使用率为:"<<backet_usage*100<<"%"<<endl;cout<<"桶的平均长度为:"<<avg_backet_len*100<<"%"<<endl;}cout<<endl;}void ClearList(){//清空哈希表，用于继续测试其他哈希函数Node *temp1,*temp2;for(int i=0;i<length;i++){temp1=head[i];while(temp1!=NULL){temp2=temp1;temp1=temp1->next;delete temp2;}head[i]=NULL;}count=0;}unsigned int MyHash(char *str){//自己设计哈希函数具体实现unsigned int hashcount=0;unsigned int x=0;int i=0;while(*str){if((i&1)==0){hashcount=((hashcount<<3)+*(str++));}else{hashcount=((hashcount<<5)+~(*str++));}if((x=hashcount&0xF0000000)!=0){hashcount=hashcount^(x>>24);hashcount=hashcount&(~x);}}return (hashcount&0x7FFFFFF);}unsigned int APHash(char *str){//AP哈希函数unsigned int hashcount=0;int i;for(i=0;*str;i++){if((i&1)==0){hashcount^=((hashcount<<7)^(*str++)^(hashcount>>3));}else{hashcount^=(~((hashcount<<11)^(*str++)^(hashcount>>5)));}}return (hashcount&0x7FFFFFFF);}unsigned int BKDRHash(char *str){//BKDR哈希函数unsigned int seed=131;unsigned int hashcount=0;while(*str){hashcount=hashcount*seed+(*str++);}return (hashcount&0x7FFFFFF);}unsigned int ELFHash(char *str){//ELF哈希函数unsigned int hashcount=0;unsigned int x=0;while(*str){hashcount=(hashcount<<4)+(*str++);if((x=hashcount&0xF0000000)!=0){hashcount^=(x>>24);hashcount&=~x;}}return hashcount;}private:Node**head;//哈希表头int length;//哈希表长int count;//读入字符串数量FILE*file;//数据读入文件头指针float backet_usage;//桶的使用率float avg_backet_len;//平均桶长};int main(){Hash hash(90000);hash.SetFile(90000);//进行10000个随机数据哈希函数性能的比较hash.HashTest(0);//BKDR,hash.HashTest(1);//ELFhash.HashTest(2);//APhash.HashTest(3);//自己设计哈希函数return 0;}。