hello-algo/codes/csharp/chapter_hashing/array_hash_map.cs

/**
 * File: array_hash_map.cs
 * Created Time: 2022-12-23
 * Author: haptear (haptear@hotmail.com)
 */

using NUnit.Framework;

namespace hello_algo.chapter_hashing
{

    /* 键值对 int->String */
    class Entry
    {
        public int key;
        public String val;
        public Entry(int key, String val)
        {
            this.key = key;
            this.val = val;
        }
    }

    /* 基于数组简易实现的哈希表 */
    class ArrayHashMap
    {
        private List<Entry?> bucket;
        public ArrayHashMap()
        {
            // 初始化一个长度为 100 的桶（数组）
            bucket = new ();
            for (int i = 0; i < 100; i++)
            {
                bucket.Add(null);
            }
        }

        /* 哈希函数 */
        private int hashFunc(int key)
        {
            int index = key % 100;
            return index;
        }

        /* 查询操作 */
        public String? get(int key)
        {
            int index = hashFunc(key);
            Entry? pair = bucket[index];
            if (pair == null) return null;
            return pair.val;
        }

        /* 添加操作 */
        public void put(int key, String val)
        {
            Entry pair = new Entry(key, val);
            int index = hashFunc(key);
            bucket[index]=pair;
        }

        /* 删除操作 */
        public void remove(int key)
        {
            int index = hashFunc(key);
            // 置为 null ，代表删除
            bucket[index]=null;
        }

        /* 获取所有键值对 */
        public List<Entry> entrySet()
        {
            List<Entry> entrySet = new ();
            foreach (Entry? pair in bucket)
            {
                if (pair != null)
                    entrySet.Add(pair);
            }
            return entrySet;
        }

        /* 获取所有键 */
        public List<int> keySet()
        {
            List<int> keySet = new ();
            foreach (Entry? pair in bucket)
            {
                if (pair != null)
                    keySet.Add(pair.key);
            }
            return keySet;
        }

        /* 获取所有值 */
        public List<String> valueSet()
        {
            List<String> valueSet = new ();
            foreach (Entry? pair in bucket)
            {
                if (pair != null)
                    valueSet.Add(pair.val);
            }
            return valueSet;
        }

        /* 打印哈希表 */
        public void print()
        {
            foreach (Entry kv in entrySet())
            {
                Console.WriteLine(kv.key + " -> " + kv.val);
            }
        }
    }


    public class array_hash_map
    {
        [Test]
        public void Test()
        {
            /* 初始化哈希表 */
            ArrayHashMap map = new ArrayHashMap();

            /* 添加操作 */
            // 在哈希表中添加键值对 (key, value)
            map.put(12836, "小哈");
            map.put(15937, "小啰");
            map.put(16750, "小算");
            map.put(13276, "小法");
            map.put(10583, "小鸭");
            Console.WriteLine("\n添加完成后，哈希表为\nKey -> Value");
            map.print();

            /* 查询操作 */
            // 向哈希表输入键 key ，得到值 value
            String? name = map.get(15937);
            Console.WriteLine("\n输入学号 15937 ，查询到姓名 " + name);

            /* 删除操作 */
            // 在哈希表中删除键值对 (key, value)
            map.remove(10583);
            Console.WriteLine("\n删除 10583 后，哈希表为\nKey -> Value");
            map.print();

            /* 遍历哈希表 */
            Console.WriteLine("\n遍历键值对 Key->Value");
            foreach (Entry kv in map.entrySet())
            {
                Console.WriteLine(kv.key + " -> " + kv.val);
            }
            Console.WriteLine("\n单独遍历键 Key");
            foreach (int key in map.keySet())
            {
                Console.WriteLine(key);
            }
            Console.WriteLine("\n单独遍历值 Value");
            foreach (String val in map.valueSet())
            {
                Console.WriteLine(val);
            }
        }
    }
}