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Description

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.

Solutions

Python3

class MyHashMap:

    def __init__(self):
        """
        Initialize your data structure here.
        """
        self.data = [-1] * 1000001

    def put(self, key: int, value: int) -> None:
        """
        value will always be non-negative.
        """
        self.data[key] = value

    def get(self, key: int) -> int:
        """
        Returns the value to which the specified key is mapped, or -1 if this map contains no mapping for the key
        """
        return self.data[key]

    def remove(self, key: int) -> None:
        """
        Removes the mapping of the specified value key if this map contains a mapping for the key
        """
        self.data[key] = -1



# Your MyHashMap object will be instantiated and called as such:
# obj = MyHashMap()
# obj.put(key,value)
# param_2 = obj.get(key)
# obj.remove(key)

Java

class MyHashMap {

    private int[] data;

    /** Initialize your data structure here. */
    public MyHashMap() {
        data = new int[1000001];
        Arrays.fill(data, -1);
    }

    /** value will always be non-negative. */
    public void put(int key, int value) {
        data[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 data[key];
    }

    /** Removes the mapping of the specified value key if this map contains a mapping for the key */
    public void remove(int key) {
        data[key] = -1;
    }
}

/**
 * Your MyHashMap object will be instantiated and called as such:
 * MyHashMap obj = new MyHashMap();
 * obj.put(key,value);
 * int param_2 = obj.get(key);
 * obj.remove(key);
 */

...