How to implement a custom indexing data structure (e.g., hash table) in Go?

To implement a custom indexing data structure like a hash table in Go, you can follow these steps:

Define a struct for the hash table and initialize its properties. In Go, a hash table can be represented as an array of linked lists, where each linked list holds the key-value pairs.

type HashTable struct {
    table []*LinkedList
    size  int
}

Create a struct for the linked list and initialize its properties. Each node in the linked list will hold a key-value pair.

type Node struct {
    key   string
    value interface{}
    next  *Node
}

type LinkedList struct {
    head *Node
}

Implement a hash function to convert keys into array indices. Go's built-in hash/fnv package can be used for this purpose.

import (
    "hash/fnv"
)

func hashCode(key string) uint32 {
    h := fnv.New32a()
    h.Write([]byte(key))
    return h.Sum32()
}

Add methods to the HashTable struct for inserting, retrieving, and deleting key-value pairs.

// Insert adds a key-value pair to the hash table
func (ht *HashTable) Insert(key string, value interface{}) {
    index := hashCode(key) % uint32(ht.size)

    if ht.table[index] == nil {
        ht.table[index] = &LinkedList{}
    }
  
    ht.table[index].Insert(key, value)
}

// Get retrieves the value associated with the given key
func (ht *HashTable) Get(key string) (interface{}, bool) {
    index := hashCode(key) % uint32(ht.size)

    if ht.table[index] == nil {
        return nil, false
    }
  
    return ht.table[index].Get(key)
}

// Delete removes the key-value pair associated with the given key
func (ht *HashTable) Delete(key string) {
    index := hashCode(key) % uint32(ht.size)

    if ht.table[index] != nil {
        ht.table[index].Delete(key)
    }
}

Implement the necessary methods for the LinkedList struct to perform operations on the linked list.

// Insert adds a node with the key-value pair to the linked list
func (ll *LinkedList) Insert(key string, value interface{}) {
    newNode := &Node{
        key:   key,
        value: value,
        next:  ll.head,
    }
    ll.head = newNode
}

// Get retrieves the value associated with the given key from the linked list
func (ll *LinkedList) Get(key string) (interface{}, bool) {
    currentNode := ll.head

    for currentNode != nil {
        if currentNode.key == key {
            return currentNode.value, true
        }
        currentNode = currentNode.next
    }

    return nil, false
}

// Delete removes the node associated with the given key from the linked list
func (ll *LinkedList) Delete(key string) {
    if ll.head == nil {
        return
    }

    if ll.head.key == key {
        ll.head = ll.head.next
        return
    }

    currentNode := ll.head

    for currentNode.next != nil {
        if currentNode.next.key == key {
            currentNode.next = currentNode.next.next
            return
        }

        currentNode = currentNode.next
    }
}

Finally, create an instance of the HashTable struct and use its methods to insert, retrieve, and delete key-value pairs.

func main() {
    ht := &HashTable{
        table: make([]*LinkedList, 10), // Initialize the array with a specific size
        size:  10,
    }

    ht.Insert("key1", "value1")
    ht.Insert("key2", "value2")

    value1, exists := ht.Get("key1")
    if exists {
        fmt.Println("Value of key1:", value1)
    }

    ht.Delete("key2")
}

This is a basic implementation of a hash table in Go. You can further extend it by handling collisions, implementing resizing, or adding additional functionalities specific to your use case.