题目

Design a HashMap without using any built-in hash table libraries.

To be specific, your design should include these functions:

  • put(key, value) : Insert a (key, value) pair into the HashMap. If the value already exists in the HashMap, update the 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) : Remove the mapping for the value key if this map contains the mapping for the key.

Example:

  1. MyHashMap hashMap = new MyHashMap();
  2. hashMap.put(1, 1);          
  3. hashMap.put(2, 2);         
  4. hashMap.get(1);            // returns 1
  5. hashMap.get(3);            // returns -1 (not found)
  6. hashMap.put(2, 1);          // update the existing value
  7. hashMap.get(2);            // returns 1 
  8. hashMap.remove(2);          // remove the mapping for 2
  9. hashMap.get(2);            // returns -1 (not found)

Note:

  • All keys and values will be in the range of [0, 1000000].
  • The number of operations will be in the range of [1, 10000].
  • Please do not use the built-in HashMap library.

题意

实现HashMap。

思路

直接开一个1000001大小的数组。

代码实现

Java

  1. class MyHashMap {
  2.     int[] hash;
  4.     /** Initialize your data structure here. */
  5.     public MyHashMap() {
  6.         hash = new int[1000001];
  7.         Arrays.fill(hash, -1);
  8.     }
  10.     /** value will always be non-negative. */
  11.     public void put(int key, int value) {
  12.         hash[key] = value;
  13.     }
  15.     /** Returns the value to which the specified key is mapped, or -1 if this map contains no mapping for the key */
  16.     public int get(int key) {
  17.         return hash[key];
  18.     }
  20.     /** Removes the mapping of the specified value key if this map contains a mapping for the key */
  21.     public void remove(int key) {
  22.         hash[key] = -1;
  23.     }
  24. }