Udemy: Master Coing Interview - Hash Tables - #78

using System;
using System.Collections.Generic;

class HashTable {
    
    public struct KeyValue {
        public string key;
        public int value;
    }
    
    public LinkedList<KeyValue>[] data;
    public int size;
    
    static void Main() {
        Console.WriteLine("Hello World!");
        
        HashTable myHashTable = new HashTable(2);
        myHashTable.Set("grapes", 10000);
        myHashTable.Set("grapes1", 10001);
        myHashTable.Set("grapes2", 10002);
        myHashTable.Set("grapes3", 10003);
        Console.WriteLine("Hash('grapes') = " + myHashTable.Get("grapes"));
        Console.WriteLine("Hash('grapes1') = " + myHashTable.Get("grapes1"));
        Console.WriteLine("Hash('grapes2') = " + myHashTable.Get("grapes2"));
        Console.WriteLine("Hash('grapes3') = " + myHashTable.Get("grapes3"));
        Console.WriteLine("Keys = " + ToString(myHashTable.Keys()));
    }
    
    public static string ToString(string[] strings) {
        string s = "{";
        int count = 0;
        foreach (string str in strings) {
            if (count > 0) {
                s += ", ";
            }
            s += str;
            count++;
        }
        s += "}";
        return s;
    }
    
    public HashTable(int size) {
        this.data = new LinkedList<KeyValue>[size];
        this.size = size;
    }
    
    public void Set(string key, int value) {
        int address = this.Hash(key);
        if (this.data[address] == null) {
            this.data[address] = new LinkedList<KeyValue>();
        }
        KeyValue kv = new KeyValue();
        kv.key = key;
        kv.value = value;
        this.data[address].AddLast(kv);
    }
    
    public int Get(string key) {
        int address = this.Hash(key);
        if (this.data[address] != null) {
            foreach (KeyValue kv in this.data[address]) {
                if (kv.key == key) {
                    return kv.value;
                }
            }
        }
        return 0;
    }
    
    public string[] Keys() {
        string[] temp = new string[100];
        int keyCount = 0;
        for (int i = 0; i < this.data.Length; i++) {
            if (this.data[i] != null) {
                foreach (KeyValue kv in this.data[i]) {
                    temp[keyCount] = kv.key;
                    keyCount++;
                }
            }
        }
        string[] keys = new string[keyCount];
        for (int i = 0; i < keyCount; i++) {
            keys[i] = temp[i];
        }
        return keys;
    }
    
    private int Hash(string key) {
        int position = key.GetHashCode() % size;
        return Math.Abs(position);
        // int hashValue = 0;
        // for (int i = 0; i < key.Length; i++) {
        //     hashValue = (hashValue + (int)key[i] * i) % this.data.Length;
        // }
        // return hashValue;
    }
}