706.design-hash-map.cpp

/*
 * @lc app=leetcode id=706 lang=cpp
 *
 * [706] Design HashMap
 *
 * https://leetcode.com/problems/design-hashmap/description/
 *
 * algorithms
 * Easy (65.22%)
 * Likes:    3480
 * Dislikes: 328
 * Total Accepted:    361.2K
 * Total Submissions: 554.4K
 * Testcase Example:  '["MyHashMap","put","put","get","get","put","get","remove","get"]\n' +
  '[[],[1,1],[2,2],[1],[3],[2,1],[2],[2],[2]]'
 *
 * 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 <= 10^6
 * At most 10^4 calls will be made to put, get, and remove.
 *
 *
 */

// @lc code=start
class MyHashMap
{
private:
    vector<unsigned int> *map;

public:
    MyHashMap() : map(new vector<unsigned int>(1000001, -1)) {}
    void put(int key, int value) { (*map)[key] = value; }
    int get(int key) { return (*map)[key]; }
    void remove(int key) { (*map)[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);
 */
// @lc code=end