Design HashMap

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

Implement the MyHashMap class:

• MyHashMap() initializes the object with an empty map.
• void put(int key, int value) inserts a (key, value) pair into the HashMap. If the key already exists in the map, update the corresponding value.
• int get(int key) returns the value to which the specified key is mapped, or -1 if this map contains no mapping for the key.
• void remove(key) removes the key and its corresponding value if the map contains the mapping for the key.

 

Example 1:

Input
["MyHashMap", "put", "put", "get", "get", "put", "get", "remove", "get"]
[[], [1, 1], [2, 2], [1], [3], [2, 1], [2], [2], [2]]
Output
[null, null, null, 1, -1, null, 1, null, -1]

Explanation
MyHashMap myHashMap = new MyHashMap();
myHashMap.put(1, 1); // The map is now [[1,1]]
myHashMap.put(2, 2); // The map is now [[1,1], [2,2]]
myHashMap.get(1);    // return 1, The map is now [[1,1], [2,2]]
myHashMap.get(3);    // return -1 (i.e., not found), The map is now [[1,1], [2,2]]
myHashMap.put(2, 1); // The map is now [[1,1], [2,1]] (i.e., update the existing value)
myHashMap.get(2);    // return 1, The map is now [[1,1], [2,1]]
myHashMap.remove(2); // remove the mapping for 2, The map is now [[1,1]] 

myHashMap.get(2); // return -1 (i.e., not found), The map is now [[1,1]] 

Solution

class MyHashMap {

int[] data;

public MyHashMap() {

data = new int[1000001];

Arrays.fill(data, -1);

}

public void put(int key, int value) {

data[key] = value;

}

public int get(int key) {

return data[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);

*/