706.MyHashMap.cs

// 706. 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]]

public class MyHashMap {
    int[] hashMap;
    public MyHashMap() {
        hashMap = new int[1000001];
        Array.Fill(hashMap,-1);
    }
    
    public void Put(int key, int value) {
        hashMap[key] = value;
    }
    
    public int Get(int key) {
        return hashMap[key];
    }
    
    public void Remove(int key) {
        hashMap[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);
 */