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I have been struggling with one of my homework questions for quite some time. I am attempting to implement a getLocation(hash1, x) method, which finds the location of the entry with key x. If such an entry does not exist, it returns the location where a new entry with key x should be stored. The question itself involves probing a Hash Map with double hashing. My attempt at implementing the method is pasted below, but something appears to be wrong. I was wondering if anyone would be able to help me correct my code. Much thanks in advance!

Java
/**
 * Searches for an entry with key equal to x (which is known to have primary
 * hash value hash1), returning the index at which it was found, or returning
 * -(a+1) where a is the index of the first empty or available slot that can
 * be used to store a new such entry.  Uses secondary hashing function 
 * h'(k) = 7 - k mod 7, where the secondary prime factor 7 is the smallest 
 * prime less than the current capacity.
 *
 * @param hash1 the precalculated hash value of the given key
 * @param x the key
 * @return index of found entry or if not found
 */
protected int getLocation(int hash1, K x) 
{

    int i = hash1;
    int hash2 = 7 - x.hashCode() % 7;        
    int present = -1;                                  

    do 
    {
        if (isAvailable(i)) 
        {                      
            if (present == -1) 
            {
                present = i;               
            }

            if (table[i] == null) 
            {
                break;              
            }
        } 

        else if (table[i].getKey().equals(x)) 
        {
            return i;                                
        }

        i = (i + hash2) % capacity;    
    } 
    while (i != hash1);                            

    return -(present + hash2);                          
}
Posted
Comments
Richard MacCutchan 20-Nov-15 5:41am    
something appears to be wrong
And what would that something be?

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