hashtable C++实现
2024-09-05 05:40:26
模仿stl，实现了开链法形式的hashtable。纯属练手，仅仅实现其基本功能，不当之处还望指正。本文为实现独立的空间配置器。
#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;
template<class value>
struct _hash_node{
value val;
_hash_node *next;
~_hash_node(){delete val;}
};
template<class value,class key,class HashFcn,class EqualKey>
class _hashtable;
template<class T1,class T2>
class _hashfcn_mod;
template<class value,class key,class HashFcn,class EqualKey>
class _hashtable_iterator{
public:
typedef _hashtable<value,key,HashFcn,EqualKey> hashtable;
typedef _hashtable_iterator<value,key,HashFcn,EqualKey> iterator;
typedef _hash_node<value> node;
typedef forward_iterator_tag iterator_category;
typedef value value_type;
typedef ptrdiff_t difference_type;
typedef size_t size_type;
typedef value& reference;
typedef value* pointer;
node* cur;
hashtable* ht;
iterator(node* n,hashtable* tab):cur(n),ht(tab){}
iterator(){}
reference operator*()const{return cur->val;}
pointer operator->()const{return &(operator*()); }
iterator& operator++(){
const node* old = cur;
cur = cur->next; //须要推断cur的next是否存在
if(!cur){ //若此bucket list已经遍历到null 则继续向下一个bucket移动
size_type bucket = ht->bkt_num(old->val);
while(!cur&& ++bucket < ht->buckets.size())
cur = ht->buckets[bucket];
}
return *this;
}
iterator operator++(int){
const iterator old = cur;
++*this;
return old;
}
bool operator==(const iterator& it)const{return cur == it.cur;}
bool operator!=(const iterator& it)const{return cur != it.cur;}
};
static const int _stl_num_primes = 28; //保存28个质数来设计表格大小
static const unsigned long _stl_prime_list[_stl_num_primes] = {
53, 97, 193, 389, 769,
1543, 3079, 6151, 12289, 24593,
49157, 98317, 196613, 393241, 786433,
1572869, 3145739, 6291469, 12582917, 25165843,
50331653, 100663319, 201326611, 402653189, 805306457,
1610612741, 3221225473ul, 4294967291ul
};
//获取大于等于n的第一个质数
inline unsigned long _stl_next_prime(unsigned long n){
const unsigned long* first = _stl_prime_list;
const unsigned long* last = _stl_prime_list + _stl_num_primes;
const unsigned long* pos = lower_bound(first,last,n);
return pos == last? *(last-1):*pos;
}
template<class value,class key,class HashFcn,class EqualKey>
class _hashtable{
public:
typedef HashFcn hasher;
typedef EqualKey key_equal;
typedef value value_type;
typedef key key_type;
typedef value_type& reference;
typedef size_t size_type;
typedef _hash_node<value> node;
typedef _hashtable_iterator<value,key,HashFcn,EqualKey> iterator;
vector<node*> buckets;
private:
hasher hash; //哈希映射函数
key_equal equals;
size_type num_elements;
private:
void initialize_buckets(size_type n){
const size_type n_buckets = next_size(n);
buckets.reserve(n_buckets);
buckets.insert(buckets.end(), n_buckets, (node*) 0);
num_elements = 0;
}
size_type next_size(size_type n)const{return _stl_next_prime(n);}
void copy_from(const _hashtable& ht) {
buckets.clear();
buckets.reserve(ht.buckets.size());
buckets.insert(buckets.end(), ht.buckets.size(), (node*) 0);
try {
for (size_type i = 0; i < ht.buckets.size(); ++i) {
if (const node* cur = ht.buckets[i]) {
node* copy = new_node(cur->val);
buckets[i] = copy;
for (node* next = cur->next; next; cur = next, next = cur->next) {
copy->next = new_node(next->val);
copy = copy->next;
}
}
}
num_elements = ht.num_elements;
}
catch(...){
clear();
}
}
node* new_node(const value_type& obj)
{
node* n = allocate((node*)0);
n->next = 0;
try {
construct(&n->val, obj);
return n;
}
catch(...){
deallocate(n);
exit(1);
}
}
template<class T>
T* allocate(T* a,ptrdiff_t size=1){
set_new_handler(0);
T* tmp = (T*)(::operator new((size_t)(size*sizeof(T))));
if(tmp == 0){
cerr<<"out of memory."<<endl;
exit(1);
}
return tmp;
}
template<class T1,class T2>
void construct(T1* p,const T2& value){new (p)T1(value);}
template<class T>
void deallocate(T* buffer){::operator delete(buffer);}
void clear(){
for (size_type i = 0; i < buckets.size(); ++i) {
node* cur = buckets[i];
while (cur != 0) {
node* next = cur->next;
delete_node(cur);
cur = next;
}
buckets[i] = 0;
}
num_elements = 0;
}
void delete_node(node* n)
{
destroy(&n->val);
deallocate(n);
}
template <class T>
void destroy(T* pointer) {
pointer->~T();
}
size_type bkt_num_key(const key_type& key)
{
return bkt_num_key(key, buckets.size());
}
size_type bkt_num_key(const key_type& key, size_t n)
{
return hash(key,n);// % n;
}
iterator insert_equal_noresize(const value_type& obj){
size_type n = bkt_num(obj);
node* first = buckets[n];
for(node* cur=first;cur;cur=cur->next){
if(equals(get_key(cur->val),get_key(obj))){
node* tmp = new_node(obj);
tmp->next = cur->next;
cur->next = tmp;
++num_elements;
returniterator(tmp,this);
}
}
node* tmp = new_node(obj);
tmp->next = first;
buckets[n] = tmp;
return iterator(tmp,this);
}
pair<iterator, bool> insert_unique_noresize(const value_type& obj){
const size_type n = bkt_num(obj);
node* first = buckets[n];
for (node* cur = first; cur; cur = cur->next)
if (equals(get_key(cur->val), get_key(obj)))
return pair<iterator, bool>(iterator(cur, this), false);
node* tmp = new_node(obj);
tmp->next = first;
buckets[n] = tmp;
++num_elements;
return pair<iterator, bool>(iterator(tmp, this), true);
}
value_type get_key(const value_type& obj){
ExtractKey<value_type> tmp;
return tmp(obj);
}
public:
size_type bucket_size(){return buckets.size();}
_hashtable(size_type n,const HashFcn& hf,const EqualKey& eql):hash(hf),equals(eql){
initialize_buckets(n);
}
_hashtable(const _hashtable& ht):hash(ht.hash),equals(ht.equals),num_elements(0){
copy_from(ht);
}
_hashtable(){clear();}
size_type bucket_count()const{return buckets.size();}
size_type max_bucket_count()const{return _stl_prime_list[_stl_num_primes - 1];}
size_type elems_in_bucket(size_type bucket)const{
size_type result = 0;
for(*node cur = buckets[bucket];cur;cur = cur->next)
result += 1;
return result;
}
size_type bkt_num(const value_type& obj)
{
return bkt_num_key(get_key(obj));
}
size_type bkt_num(const value_type& obj, size_t n) const
{
return bkt_num_key(get_key(obj), n);
}
void resize(size_type num_elements_hint){
_hashfcn_mod<value_type,value_type> hashfcn_mod;
const size_type old_n = buckets.size();
if(num_elements_hint > old_n){
const size_type n = next_size(num_elements_hint);
if(n > old_n){
vector<node*> tmp(n,(node*)0);
try{
for(size_type bucket=0;bucket<old_n;++bucket){
node* first = buckets[bucket];
while(first){
size_type new_bucket = hashfcn_mod(first->val,n);
buckets[bucket] = first->next;
first->next = tmp[new_bucket];
tmp[new_bucket] = first;
first = buckets[bucket];
}
}
buckets.swap(tmp);
}
catch(...){
for(size_type bucket=0;bucket<tmp.size();++bucket){
while(tmp[bucket]){
node* next = tmp[bucket]->next;
delete_node(tmp[bucket]);
tmp[bucket] = next;
}
}
throw;
}
}
}
}
pair<iterator,bool> insert_unique(const value_type& obj){
resize(num_elements+1);
return insert_unique_noresize(obj);
}
iterator insert_equal(const value_type& obj)
{
resize(num_elements + 1);
return insert_equal_noresize(obj);
}
iterator begin()
{
for (size_type n = 0; n < buckets.size(); ++n)
if (buckets[n])
return iterator(buckets[n], this);
return end();
}
iterator end() { return iterator(0, this); }
size_type erase(const key_type& key)
{
const size_type n = bkt_num_key(key);
node* first = buckets[n];
size_type erased = 0;
if (first) {
node* cur = first;
node* next = cur->next;
while (next) {
if (equals(get_key(next->val), key)) {
cur->next = next->next;
delete_node(next);
next = cur->next;
++erased;
--num_elements;
}
else {
cur = next;
next = cur->next;
}
}
if (equals(get_key(first->val), key)) {
buckets[n] = first->next;
delete_node(first);
++erased;
--num_elements;
}
}
return erased;
}
void erase(const iterator& it)
{
if (node* const p = it.cur) {
const size_type n = bkt_num(p->val);
node* cur = buckets[n];
if (cur == p) {
buckets[n] = cur->next;
delete_node(cur);
--num_elements;
}
else {
node* next = cur->next;
while (next) {
if (next == p) {
cur->next = next->next;
delete_node(next);
--num_elements;
break;
}
else {
cur = next;
next = cur->next;
}
}
}
}
}
reference find_or_insert(const value_type& obj){
resize(num_elements + 1);
size_type n = bkt_num(obj);
node* first = buckets[n];
for (node* cur = first; cur; cur = cur->next)
if (equals(get_key(cur->val), get_key(obj)))
return cur->val;
node* tmp = new_node(obj);
tmp->next = first;
buckets[n] = tmp;
++num_elements;
return tmp->val;
}
iterator find(const key_type& key){
size_type n = bkt_num_key(key);
node* first;
for ( first = buckets[n];first && !equals(get_key(first->val), key);
first = first->next);
return iterator(first, this);
}
void erase(iterator first, iterator last){
size_type f_bucket = first.cur ? bkt_num(first.cur->val) : buckets.size();
size_type l_bucket = last.cur ? bkt_num(last.cur->val) : buckets.size();
if (first.cur == last.cur)return;
else if (f_bucket == l_bucket)erase_bucket(f_bucket, first.cur, last.cur);
else {
erase_bucket(f_bucket, first.cur, 0);
for (size_type n = f_bucket + 1; n < l_bucket; ++n)
erase_bucket(n, 0);
if (l_bucket != buckets.size())
erase_bucket(l_bucket, last.cur);
}
}
};
/*****************************************************
此函数对象用于定义映射函数。依据自己的需求能够定义线性探測、
二次线性探測或者自己定义函数
***********************************************************/
template<class T1,class T2>
class _hashfcn_mod{ //简单取余映射
public:
T1 operator()(T1 value,T2 size){ //value为key值 size为bucket长度
return value % size;
}
};
/*************************************************************
推断键值是否相等的函数，可自己定义
*************************************************************/
template<class T>
class _key_equal{
public:
bool operator()(T t1,T t2){
return t1 == t2;
}
};
/************************************************************
从节点中取出键值的方法。可自己定义
***********************************************************/
template<class T>
class ExtractKey{ //从节点取出键值
public:
T operator()(const T& tmp){
identity<T> id;
return id(tmp);
}
};
void test1(){
_hashfcn_mod<int,int> hashfcn;
_key_equal<int> keyequal;
_hashtable<int,int,_hashfcn_mod<int,int>,_key_equal<int>> hashtab(20,hashfcn,keyequal);
hashtab.insert_unique(15);
hashtab.insert_unique(14);
hashtab.insert_unique(13);
hashtab.insert_unique(12);
_hashtable<int,int,_hashfcn_mod<int,int>,_key_equal<int>>::iterator iter;
for(iter = hashtab.begin();iter!= hashtab.end();++iter)
cout<<*iter<<" ";
cout<<endl;
hashtab.erase(12);
for(iter = hashtab.begin();iter!= hashtab.end();++iter)
cout<<*iter<<" ";
cout<<endl;
hashtab.erase(hashtab.find(13));
for(iter = hashtab.begin();iter!= hashtab.end();++iter)
cout<<*iter<<" ";
cout<<endl;
}
int main(){
test1();
}最新文章
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