Design HashMap

LeetCode Q 706 - Design HashMap

Design a HashMap without using any built-in hash table libraries.

To be specific, your design should include these functions:

• put(key, value) : Insert a (key, value) pair into the HashMap. If the value already exists in the HashMap, update the value.
• get(key): Returns the value to which the specified key is mapped, or -1 if this map contains no mapping for the key.
• remove(key) : Remove the mapping for the value key if this map contains the mapping for the key.

Example:
MyHashMap hashMap = new MyHashMap();
hashMap.put(1, 1); hashMap.put(2, 2);
hashMap.get(1); // returns 1
hashMap.get(3); // returns -1 (not found)
hashMap.put(2, 1); // update the existing value
hashMap.get(2); // returns 1
hashMap.remove(2); // remove the mapping for 2
hashMap.get(2); // returns -1 (not found)

Note:

• All keys and 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 HashMap library.

Solution

Code:

class MyHashMap {

	int[] arr;

	/ ** Initialize your data structure here. * /
	public MyHashMap() {
		arr = new int[1000001];
		Arrays.fill(arr, -1);
	}
	
	/ ** value will always be non-negative. * /
	public void put(int key, int value) {
		arr[key] = value;
	}
	
	/ ** Returns the value to which the specified key is mapped, or -1 if this map contains no mapping for the key * /
	public int get(int key) {
		return arr[key];
	}
	
	/** Removes the mapping of the specified value key if this map contains a mapping for the key */
	public void remove(int key) {
		arr[key] = -1;
	}
}