Thread: Insert Items in Hash Table Container.

You have KEYTYPE, presumably for the key type, but then you use std::string in the functions as the type of the key. Either make it generic or specialize it for string keys.

You need a hashing function. Either allow the user to specify one, or if you start off focusing on strings supply your own (search for a good hash function for strings).

Regardless, the hash function should be separate from your insert function. Get the hashed value and then just push the value onto the appropriate list based on the result of the hash. That should be all the insert function needs to do - maybe one or two lines of code.

you mean what I use std::string means that one?

Code:

void        insertItem( const string& key, const VALUETYPE& value );

Can you give me some advise how to create a hash function?

What is the collate for?

Code:

const collate<char>& coll = use_facet<collate<char> > ( locale() )

collate should be a class name? right?

I am still thinking how I can insert a string and an int inside the function insert.

Can anyone give me some suggest?

Here is my expected output:
Bucket #0 contains: [Carol,29]
Bucket #1 contains:
Bucket #2 contains: [Fred,45]
Bucket #3 contains:
Bucket #4 contains: [Lori,38]
Bucket #5 contains:
Bucket #6 contains:
Bucket #7 contains: [Sue,20]
Bucket #8 contains: [Jane,26] [Joe,18]
Bucket #9 contains:
Bucket #10 contains:
Bucket #11 contains: [Dave,23]
Bucket #12 contains:
Bucket #13 contains:
Bucket #14 contains:
Bucket #15 contains: [James,27]
Bucket #16 contains: [Mark,34]
Bucket #17 contains: [Beth,25]
Bucket #18 contains:
Bucket #19 contains:


Dave's value is: 23
Sue's value is: 20
Mark's value is: 34
Fred's value is: 45
Jane's value is: 26
Carol's value is: 29
Joe's value is: 18
Lori's value is: 38
James' value is: 27
Beth's value is: 25

and this is the HashTableTest.cpp

Code:

//HashTableTest.cpp
#include <cstdlib>
#include <iostream>

#include "hashtable.h"

using namespace std;

int main() {

    HashTable<string,int> hashTable;

    //hashTable.dump();

    hashTable.insertItem( "Dave", 23 );
    hashTable.insertItem( "Sue", 20 );
    hashTable.insertItem( "Mark", 34 );
    hashTable.insertItem( "Fred", 45 );
    hashTable.insertItem( "Jane", 26 );
    hashTable.insertItem( "Carol", 29 );
    hashTable.insertItem( "Joe", 18 );
    hashTable.insertItem( "Lori", 38 );
    hashTable.insertItem( "James", 27 );
    hashTable.insertItem( "Beth", 25 );

    cout << endl << endl;

    hashTable.dump();

    cout << endl << endl;

    cout << "Dave's value is: " << hashTable.getItem( "Dave" ) << endl;
    cout << "Sue's value is: " << hashTable.getItem( "Sue" ) << endl;
    cout << "Mark's value is: " << hashTable.getItem( "Mark" ) << endl;
    cout << "Fred's value is: " << hashTable.getItem( "Fred" ) << endl;
    cout << "Jane's value is: " << hashTable.getItem( "Jane" ) << endl;
    cout << "Carol's value is: " << hashTable.getItem( "Carol" ) << endl;
    cout << "Joe's value is: " << hashTable.getItem( "Joe" ) << endl;
    cout << "Lori's value is: " << hashTable.getItem( "Lori" ) << endl;
    cout << "James' value is: " << hashTable.getItem( "James" ) << endl;
    cout << "Beth's value is: " << hashTable.getItem( "Beth" ) << endl;


    return EXIT_SUCCESS;
}

My question is, for inserting ( "Dave", 23)

How I can let the computer knows this items should be place in Bucket #10?
Any algorithm can do it?
thanks for advise.

Should I use Dave % 20 to figure out this problem?

for my insert method:

Code:

template <typename KEYTYPE, typename VALUETYPE>
void HashTable<KEYTYPE,VALUETYPE>::insertItem( const string& key, const VALUETYPE& value ) {
	key = &key.push_front();        //push the address of key to the private attritbute key.
	
	value = &value.push_front();  //push the address of value to the private attribute value.
}

I think it is not suitable to put the algorithm inside the insert function, I should create another function to fix this problem, right?
Also, do you think this is a good way to insert the key and the item.

Code:

key = &key.push_front();        //push the address of key to the private attritbute key.
	
	value = &value.push_front();  //push the address of value to the private attribute value.

Some of my questions may be annoyed u guys, but i am really want to learn it because i am so interest in the data structures.

Appericate it.

Do you think I should declear myHashFunction inside the private section?
I think those code from you should work

Code:

int hashFunc ( char *key ) {
  int res = 0;
  while ( *key ) res += *key++;
  return key % 20;
}