LeetCode-706. Design HashMap

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问题描述

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 :

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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.

解答

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/*
 * @Description: 706. Design HashMap
 * @Author: libk
 * @Github: https://github.com/libk
 */

/**
 * Your MyHashMap object will be instantiated and called as such:
 * var obj = new MyHashMap()
 * obj.put(key,value)
 * var param_2 = obj.get(key)
 * obj.remove(key)
 */
const MyHashMap = function () {
  this.BASE = 769
  this.data = new Array(this.BASE).fill(0).map(() => [])
}

/**
 * @param {number} key
 * @param {number} value
 * @return {void}
 */
MyHashMap.prototype.put = function (key, value) {
  let index = this.hash(key)
  let node = this.data[index]
  for (let i = 0; i < node.length; i++) {
    if (node[i][0] === key) {
      node[i][1] = value
      return
    }
  }
  node.push([key, value])
}

/**
 * @param {number} key
 * @return {number}
 */
MyHashMap.prototype.get = function (key) {
  let index = this.hash(key)
  let node = this.data[index]
  for (let i = 0; i < node.length; i++) {
    if (node[i][0] === key) {
      return node[i][1]
    }
  }
  return -1
}

/**
 * @param {number} key
 * @return {void}
 */
MyHashMap.prototype.remove = function (key) {
  let index = this.hash(key)
  let node = this.data[index]
  for (let i = 0; i < node.length; i++) {
    if (node[i][0] === key) {
      node.splice(i, 1)
    }
  }
}

/**
 * @param {number} key
 * @return {number}
 */
MyHashMap.prototype.hash = function (key) {
  return key % this.BASE
}