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template <class TYPE>
class Table {
public:
Table() {}
virtual bool update(const string& key, const TYPE& value) = 0;
virtual bool remove(const string& key) = 0;
virtual bool find(const string& key, TYPE& value) = 0;
virtual ~Table() {}
};
template <class TYPE>
class HashTable :public Table<TYPE> {
// This is the internal structure for array elements for hastable
struct Record {
TYPE data_; // data per array element
string key_;//key to lookup for data element
Record* next_; // next record to create linkly linked list for bucketing
// Constructor to set values of Record
Record(const string& key, const TYPE& data) {
key_ = key;
data_ = data;
next_=nullptr;
}
//Returns key of Record
string getKey() const {
return key_;
}
//Sets key of Record
string setKey(string key) {
key_=key;
}
//Returns data member of Record
TYPE getData() const {
return data_;
}
//Sets data member of Record
void setData(TYPE data) {
data_=data;
}
//Gets next element in linked list for bucketing
Record *getNext() const {
return next_;
}
//Sets next element in linked list for bucketing
void setNext(Record *next) {
next_ = next;
}
};
Record** table_; //the table
int size_;//size_
int cap;//max number of records allowed in table
std::hash<std::string> hash;//hash function used
public:
HashTable(int maxExpected);
HashTable(const HashTable& other);
HashTable(HashTable&& other);
int numRecords();
bool isEmpty();
virtual bool update(const string& key, const TYPE& value);
virtual bool remove(const string& key);
virtual bool find(const string& key, TYPE& value);
virtual const HashTable& operator=(const HashTable& other);
virtual const HashTable& operator=(HashTable&& other);
virtual ~HashTable();
};
/* none of the code in the function definitions below are correct. You can replace what you need
*/
//returns size of table
template <class TYPE>
int HashTable<TYPE>::numRecords() {
return size_;
}
//returns if hashtable has no records been inserted
template <class TYPE>
bool HashTable<TYPE>::isEmpty(){
return size_==0;
}
//Constructor that allocates memory equal to passed amount in maxExpected and sets hashtable to empty state
template <class TYPE>
HashTable<TYPE>::HashTable(int maxExpected) : Table<TYPE>() {
int size_=0;
table_=new Record*[maxExpected]();
cap=maxExpected;
}
//Copy Constructor that creates a copy of passed hashtable as argument to create a new copy of including memory allocations
template <class TYPE>
HashTable<TYPE>::HashTable(const HashTable<TYPE>& other) {
table_ = new Record*[other.cap];
size_=other.size_;
hash = other.hash;
cap=other.cap;
for(int i=0;i<other.cap;i++){
if(other.table_[i]==nullptr){
table_[i]=nullptr;
continue;
}
//need to move over elements from next pointers of other.table's element at i for bucketing to work
swap(table_[i],other.table_[i]);
}
}
//Move constructor that moves the hashtable passed into the current table being constructed
template <class TYPE>
HashTable<TYPE>::HashTable(HashTable<TYPE>&& other) {
swap(size_,other.size_);
swap(cap,other.cap);
swap(table_,other.table_);
swap(hash,other.hash);
}
//Updates record with the string passed to the new data for the record's data element and returns true if found/updated otherwise false
template <class TYPE>
bool HashTable<TYPE>::update(const string& key, const TYPE& value) {
int hashvalue=hash(key)%cap;
Record* prev=nullptr;
Record* entry=table_[hashvalue];
while (entry != nullptr && entry->getKey() != key) {
prev=entry;
entry=entry->getNext();
}
if (entry == nullptr) {
entry = new Record(key, value);
if (prev == nullptr) {
// insert as first bucket
table_[hashvalue] = entry;
} else {
prev->setNext(entry);
}
} else {
// just update the value
entry->setData(value);
}
size_++;
return true;
}
//Removes the record with the string passed for the key value and returns true if removed otherwise false if not found
template <class TYPE>
bool HashTable<TYPE>::remove(const string& key) {
int hashValue = hash(key)%cap;
Record *prev = nullptr;
Record *entry = table_[hashValue];
while (entry != nullptr && entry->getKey() != key) {
prev = entry;
entry = entry->getNext();
}
if (entry == nullptr) {
// key not found
return false;
}
else {
if (prev == nullptr) {
// remove first bucket of the list
table_[hashValue] = entry->getNext();
} else {
prev->setNext(entry->getNext());
}
delete entry;
}
size_--;
return true;
}
//Finds value in table and updates with the value passed if found returns true otherwise false
template <class TYPE>
bool HashTable<TYPE>::find(const string& key, TYPE& value) {
int hashValue = hash(key)%cap;
Record* entry =table_[hashValue];
while (entry != nullptr) {
if (entry->getKey() == key) {
value=entry->getData();
return true;
}
entry = entry->getNext();
}
return false;
}
//Copy Assignment Operator creates copy of hashtable passed into current hashtable
template <class TYPE>
const HashTable<TYPE>&HashTable<TYPE>::operator=(const HashTable<TYPE>& other) {
if (table_) {
delete[] table_;
}
table_ = new Record*[other.cap];
size_=other.size_;
hash = other.hash;
cap=other.cap;
return *this;
}
//Moves Assignment Operator which moves passed hashtable into current hashtable
template <class TYPE>
const HashTable<TYPE>& HashTable<TYPE>::operator=(HashTable<TYPE>&& other) {
swap(size_,other.size_);
swap(table_,other.table_);
swap(hash,other.hash);
swap(cap,other.cap);
return *this;
}
//Destructor this destroys the hashtable when it goes out of scope or is called directly
template <class TYPE>
HashTable<TYPE>::~HashTable() {
// destroy all buckets one by one
for (int i = 0; i < cap; ++i) {
Record *entry = table_[i];
while (entry != nullptr) {
Record *prev = entry;
entry = entry->getNext();
delete prev;
}
table_[i] = nullptr;
}
// destroy the hash table
delete [] table_;
}
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