basic implementation of hashmap with linked list as storing the bucket

Author: hitmanbuzz

map.go

@@ -0,0 +1,161 @@
+//go:build ignore
+
+package main
+
+import "fmt"
+
+const MAP_SIZE = 100
+
+type HashTable[T any] struct {
+	key   string
+	value T
+}
+
+type Node[T any] struct {
+	data HashTable[T]
+	next *Node[T]
+}
+
+type HashMap[T any] struct {
+	arr  [MAP_SIZE]*Node[T]
+	size int
+}
+
+func NewMap[T any]() *HashMap[T] {
+	var items [MAP_SIZE]*Node[T]
+	return &HashMap[T]{
+		arr:  items,
+		size: 0,
+	}
+}
+
+func (m *HashMap[T]) Insert(k string, v T) {
+	idx := ComputeHash(k) % MAP_SIZE
+	node := &Node[T]{
+		data: HashTable[T]{
+			key:   k,
+			value: v,
+		},
+		next: m.arr[idx],
+	}
+
+	m.arr[idx] = node
+	m.size++
+}
+
+func (m *HashMap[T]) Get(k string) *T {
+	idx := ComputeHash(k) % MAP_SIZE
+	curr := m.arr[idx]
+
+	for curr != nil {
+		table := curr.data
+		if table.key == k {
+			return &table.value
+		}
+
+		curr = curr.next
+	}
+
+	return nil
+}
+
+func (m *HashMap[T]) Delete(k string) bool {
+	isDelete := false
+	idx := ComputeHash(k) % MAP_SIZE
+	curr := m.arr[idx]
+
+	if curr == nil {
+		return false
+	}
+
+	if curr.data.key == k {
+		m.arr[idx] = curr.next
+		m.size--
+		return true
+	}
+
+	for curr.next != nil {
+		table := curr.next.data
+		if table.key == k {
+			// found the key, now remove it and shift all the later nodes towards it
+			curr.next = curr.next.next
+			m.size--
+			return true
+		}
+		curr = curr.next
+	}
+
+	return isDelete
+}
+
+// modulo the hash result with the size of the array
+func ComputeHash(input string) uint {
+	const p uint = 31
+	const m uint = 1e9 + 9
+	var hashValue uint = 0
+	var pPow uint = 1
+	for _, c := range input {
+		hashValue = (hashValue + (uint(c)-uint('a')+1)*pPow) % m
+		pPow = (pPow * p) % m
+	}
+
+	return hashValue
+}
+
+func main() {
+	hashMap := NewMap[int]()
+	hashMap.Insert("John", 18)
+	hashMap.Insert("Abraham", 24)
+	hashMap.Insert("Jack", 30)
+	hashMap.Insert("Luis", 50)
+	hashMap.Insert("Maple", 25)
+	hashMap.Insert("Ron", 20)
+
+	john := hashMap.Get("John")
+	if john == nil {
+		fmt.Println("Key: `John` not found")
+	} else {
+		fmt.Printf("For John: %d\n", *john)
+	}
+
+	abra := hashMap.Get("Abraham")
+	if abra == nil {
+		fmt.Println("Key: `Abraham` not found")
+	} else {
+		fmt.Printf("For Abraham: %d\n", *abra)
+	}
+
+	luis := hashMap.Get("Luis")
+	if luis == nil {
+		fmt.Println("Key: `Luis` not found")
+	} else {
+		fmt.Printf("For Luis: %d\n", *luis)
+	}
+
+	maple := hashMap.Get("Maple")
+	if maple == nil {
+		fmt.Println("Key: `Maple` not found")
+	} else {
+		fmt.Printf("For Maple: %d\n", *maple)
+	}
+
+	rohn := hashMap.Get("Apple")
+	if rohn == nil {
+		fmt.Println("Key: `Apple` not found")
+	} else {
+		fmt.Printf("For Apple: %d\n", *rohn)
+	}
+
+	status := hashMap.Delete("Jack")
+	if !status {
+		fmt.Println("Key not found, so unable to delete it")
+	} else {
+		// delete so not found in the table
+		jack := hashMap.Get("Jack")
+		if jack == nil {
+			fmt.Println("Key: `Jack` not found")
+		} else {
+			fmt.Printf("For Jack: %d\n", *jack)
+		}
+	}
+}