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HashSetDesign.java
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HashSetDesign.java
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package Leetcode;
import java.util.LinkedList;
/**
* @author kalpak
*
* Design a HashSet without using any built-in hash table libraries.
*
* To be specific, your design should include these functions:
*
* add(value): Insert a value into the HashSet.
* contains(value) : Return whether the value exists in the HashSet or not.
* remove(value): Remove a value in the HashSet. If the value does not exist in the HashSet, do nothing.
*
*
* Example:
*
* MyHashSet hashSet = new MyHashSet();
* hashSet.add(1);
* hashSet.add(2);
* hashSet.contains(1); // returns true
* hashSet.contains(3); // returns false (not found)
* hashSet.add(2);
* hashSet.contains(2); // returns true
* hashSet.remove(2);
* hashSet.contains(2); // returns false (already removed)
*
*
* Note:
*
* All values will be in the range of [0, 1000000].
* The number of operations will be in the range of [1, 10000].
* Please do not use the built-in HashSet library.
*/
public class HashSetDesign {
private Bucket[] buckets;
private int keyRange;
public HashSetDesign() {
keyRange = 769;
buckets = new Bucket[keyRange];
for(int i = 0; i < keyRange; i++) {
buckets[i] = new Bucket();
}
}
public void add(int key) {
int bucketIdx = getHash(key);
buckets[bucketIdx].insert(key);
}
public void remove(int key) {
int bucketIdx = getHash(key);
buckets[bucketIdx].delete(key);
}
/** Returns true if this set contains the specified element */
public boolean contains(int key) {
int bucketIdx = getHash(key);
return buckets[bucketIdx].isPresent(key);
}
private int getHash(int key) {
return (key % keyRange);
}
class Bucket {
private LinkedList<Integer> container;
public Bucket() {
container = new LinkedList<>();
}
public void insert(Integer key) {
int idx = container.indexOf(key);
if(idx == - 1) {
container.addFirst(key);
}
}
public void delete(Integer key) {
container.remove(key);
}
public boolean isPresent(Integer key) {
int idx = container.indexOf(key);
return (idx != -1);
}
}
public static void main(String[] args) {
HashSetDesign obj = new HashSetDesign();
obj.add(1);
System.out.println(obj.contains(1));
System.out.println(obj.contains(2));
}
}