/*
Closed Hash table for storing bank accounts
*/


class account
{
    String owner;  // owner of bank account
    int ssn;       // social security number 
    double balance; // current balance;
    String address;  // other info ...    
    static double interest_rate = 0.01;

    void withdraw(double amt) { balance -= amt; }
    void deposit(double amt) { balance += amt; }

    public account(String o, int s) // constructor
    {  owner=o;  ssn=s;  balance = 100; }

} // class account



// using the sum of the ascii values of

public class closehash
{
    account[] Table;
    boolean[] occupied;
    int size = 0;  // number of current entries in table
    public closehash(int n) // constructor
    { 
      Table = new account[n];    // default set to null
      occupied = new boolean[n];  // default set to false
    }

    public int hash(String key)
    {
	// compute sum of asscii values
	int sum = 0;
	for (int i=0;i<key.length();i++) sum += (int)key.charAt(i);
	return sum % Table.length;
    }

    private int rehash(int h) { return (h+1) % Table.length; }


    // insert account 
    public void insert(account A) throws Exception
    {
	if (size==Table.length) throw new Exception("table full");
	int i = hash(A.owner);
	while (Table[i]!=null) i = rehash(i);
	Table[i] = A;
	occupied[i] = true;
	size++;
    }

    // returns either pointer to account with correct id, or null
    public account lookup(String id)
    {
	int i = hash(id);
	boolean stop = false;
	account A = null;
	int counter = 0; 
	while( !stop )
        {
	    if (Table[i]==null)
		{ if (occupied[i]) i = rehash(i); else stop=true; }
	    else
		{
		    if (Table[i].owner.equals(id))
			{ stop=true; A = Table[i]; }
		    else i = rehash(i);
		}
	    if (++counter > Table.length) stop = true;
		
	} // while
	return A;
    } // lookup


    public void delete(String id)
    {
	int i = hash(id);
	boolean stop = false;
	int counter = 0; 
	while( !stop )
        {
	    if (Table[i]==null)
		{ if (occupied[i]) i = rehash(i); else stop=true; }
	    else
		{
		    if (Table[i].owner.equals(id))
			{ stop=true; Table[i] = null; size--; }
		    else i = rehash(i);
		}
	    if (++counter > Table.length) stop = true;
	} // while
    }
    

    public static void main(String[] args) throws Exception
    {
	closehash HT = new closehash(100);
	HT.insert(new account("mary",123896741));
	HT.insert(new account("harry",761908765));
	HT.insert(new account("larz",123459765));
	HT.insert(new account("narx",987654321));
	System.out.println(HT.lookup("larz"));
	HT.delete("larz");
	System.out.println(HT.lookup("narx"));
	System.out.println(HT.lookup("larz"));	
    }

} // closehash