LeetCode 706. Design HashMap

Design a HashMap without using any built-in hash table libraries. You may not use set() or dict().

Implement the MyHashMap class:

• MyHashMap() initializes the object with an empty map.
• put(key, value) inserts a (key, value) pair into the HashMap. If the key already exists in the map, update the corresponding 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) removes the key and its corresponding value if the map contains the mapping for the key.

Examples

Example 1

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

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

Constraints

• 0 <= key, value <= 1,000,000
• At most 10,000 calls will be made to put, get, and remove.

How the tests work: each test is a sequence of calls. operations[i] is the method called with arguments[i]; the first entry constructs the class. The expected output lists what every call returns — null for the constructor and for methods that return nothing.