[LeetCode] 706. Design HashMap

bergwhite 发布于2019-08-19 11:12 / 292人阅读

Problem

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:

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

Solution

class MyHashMap {
        
    class ListNode {
        ListNode next;
        int key, val;
        
        ListNode(int key, int value) {
            this.key = key;
            this.val = value;
        }
    }
    
    class Bucket {
        final ListNode head = new ListNode(-1, -1);
    }
    
    final int size = 10000;
    final Bucket[] buckets = new Bucket[size];

    /** Initialize your data structure here. */
    public MyHashMap() {
        
    }
    
    //used to find the bucket
    private int hash(int key) {
        return key % size;
    }
    
    //used to find node by key in certain bucket
    private ListNode findNode(Bucket bucket, int key) {
        ListNode head = bucket.head;
        ListNode node = head;
        while (head != null && head.key != key) {
            //when head == null, or head.key == key, return its previous node
            node = head;
            head = head.next;
        }
        return node;
    }
    
    /** value will always be non-negative. */
    public void put(int key, int value) {
        int i = hash(key);
        if (buckets[i] == null) buckets[i] = new Bucket();
        ListNode pre = findNode(buckets[i], key);
        if (pre.next == null) {
            pre.next = new ListNode(key, value);
        } else {
            pre.next.val = value;
        }
    }
    
    /** Returns the value to which the specified key is mapped, or -1 if this map contains no mapping for the key */
    public int get(int key) {
        int i = hash(key);
        if (buckets[i] == null) return -1;
        ListNode pre = findNode(buckets[i], key);
        if (pre.next == null) {
            return -1;
        } else {
            return pre.next.val;
        }
    }
    
    /** Removes the mapping of the specified value key if this map contains a mapping for the key */
    public void remove(int key) {
        int i = hash(key);
        if (buckets[i] == null) return;
        ListNode pre = findNode(buckets[i], key);
        if (pre.next == null) return;
        else pre.next = pre.next.next;
    }

}

/**
 * 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);
 */

混合云超融合服务器服务器支持706 LeetCode LeetCode_String leetcode_35_SearchIn

文章版权归作者所有，未经允许请勿转载,若此文章存在违规行为，您可以联系管理员删除。

转载请注明本文地址：https://www.ucloud.cn/yun/77182.html

Leetcode PHP题解--D75 706. Design HashMap

摘要：题目链接题目分析自行设计一个。需要实现题目内指定的函数。思路我觉得这个没什么好说的吧最终代码若觉得本文章对你有用，欢迎用爱发电资助。 D75 706. Design HashMap 题目链接 706. Design HashMap 题目分析自行设计一个hashmap。需要实现题目内指定的函数。思路我觉得这个没什么好说的吧… 最终代码

sf190404 2019-07-01 12:50 评论0 收藏0
359. Logger Rate Limiter & 362. Design Hit Cou

摘要：题目链接和基本一样，都可以用，但是大了之后会有很多无效的时间保存在里面，要的话，可能需要遍历或者用辅助，时间复杂度超过，所以用一个来做，每次根据新的改变。 359. Logger Rate Limiter 题目链接：https://leetcode.com/problems... 和Design Hit Counter基本一样，都可以用hashmap，但是timestamp大了之后会有...

go4it 2019-08-14 17:27 评论0 收藏0
[LeetCode] 642. Design Search Autocomplete System

Problem Design a search autocomplete system for a search engine. Users may input a sentence (at least one word and end with a special character #). For each character they type except #, you need to r...

MartinHan 2019-08-16 13:40 评论0 收藏0
[LeetCode/LintCode] Design Twitter/Mini Twitter

摘要：首先建立按时间戳从大到小排列的，找到中的，出其中在中存在的，把每一个的推特链表放入，再从中取头十条推特的放入结果数组。 Design Twitter Note 建立两个HashMap，一个存user，一个存tweets。以及整型的时间戳timestamp。user的k-v pair是userId-follower_set，tweets的k-v pair是userId-tweets_li...

honmaple 2019-08-14 15:31 评论0 收藏0
[LeetCode] 588. Design In-Memory File System

Problem Design an in-memory file system to simulate the following functions: ls: Given a path in string format. If it is a file path, return a list that only contains this files name. If it is a direc...

SHERlocked93 2019-08-16 13:57 评论0 收藏0