Hash Map Algorithm
Ideally, the hash function will assign each key to a unique bucket, but most hash table designs use an imperfect hash function, which might cause hash collisions where the hash function generates the same index for more than one key. In computing, a hash table (hash map) is a data structure that implements an associative array abstract data type, a structure that can map keys to values. In January 1953, Hans Peter Luhn write an internal IBM memorandum that used hashing with chaining. gene Amdahl, Elaine M. McGraw, Nathaniel Rochester, and Arthur Samuel implemented a plan use hashing at about the same time. open addressing with linear probing (relatively prime stepping) is credited to Amdahl, but Ershov (in Russia) had the same idea.
package DataStructures.HashMap.Hashing;
class HashMap {
private int hsize;
private LinkedList[] buckets;
public HashMap(int hsize) {
buckets = new LinkedList[hsize];
for (int i = 0; i < hsize; i++) {
buckets[i] = new LinkedList();
// Java requires explicit initialisaton of each object
}
this.hsize = hsize;
}
public int hashing(int key) {
int hash = key % hsize;
if (hash < 0)
hash += hsize;
return hash;
}
public void insertHash(int key) {
int hash = hashing(key);
buckets[hash].insert(key);
}
public void deleteHash(int key) {
int hash = hashing(key);
buckets[hash].delete(key);
}
public void displayHashtable() {
for (int i = 0; i < hsize; i++) {
System.out.printf("Bucket %d :", i);
buckets[i].display();
}
}
}
