706. Design HashMap

Easy

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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]]

Constraints:

• 0 <= key, value <= 106

• At most 104 calls will be made to put, get, and remove.

class MyHashMap:

    def __init__(self):
        self.size = 10**4
        self.arr = [None]*self.size
        
    def hash(self, key):
        return key % self.size

    def put(self, key: int, value: int) -> None:
        h = self.hash(key)
        if self.arr[h] is not None:
            for index, ls in enumerate(self.arr[h]):
                k,v = ls
                if key == k:
                    self.arr[h][index] = [k, value]
                    return
            self.arr[h].append([key, value])
        else:
            self.arr[h] = [[key, value]]
                    

    def get(self, key: int) -> int:
        ls = self.arr[self.hash(key)]
        if not ls:
            return -1
        for k,v in ls:
            if k == key:
                return v
        return -1

    def remove(self, key: int) -> None:
        h = self.hash(key)
        ls = self.arr[h]
        if not ls:
            return
        for index, l in enumerate(ls):
            k,v = l
            if k == key:
                del self.arr[h][index]


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