doubly_linked_list.go

package main

import "fmt"

type Node struct {
    data interface{}
    prev *Node
    next *Node
}

type DoublyLinkedList struct {
    head *Node
}

func (list *DoublyLinkedList) IsEmpty() bool {
    return list.head == nil
}

func (list *DoublyLinkedList) InsertAtHead(data interface{}) {
    new := &Node{data: data}
    if list.IsEmpty() {
        list.head = new
    } else {
        new.next = list.head
        list.head.prev = new
        list.head = new
    }
}

func (list *DoublyLinkedList) InsertAtTail(data interface{}) {
    new := &Node{data: data}
    if list.IsEmpty() {
        list.head = new
    } else {
        current := list.head
        for current.next != nil {
            current = current.next
        }
        current.next = new
        new.prev = current
    }
}

func (list *DoublyLinkedList) DeleteAtHead() {
    if list.IsEmpty() {
        fmt.Println("Linked list is empty. No node to delete.")
    } else {
        if list.head.next == nil {
            list.head = nil
        } else {
            list.head = list.head.next
            list.head.prev = nil
        }
    }
}

func (list *DoublyLinkedList) DeleteAtTail() {
    if list.IsEmpty() {
        fmt.Println("Linked list is empty. No node to delete.")
    } else {
        if list.head.next == nil {
            list.head = nil
        } else {
            current := list.head
            for current.next != nil {
                current = current.next
            }
            current.prev.next = nil
        }
    }
}

func (list *DoublyLinkedList) DisplayForward() {
    if list.IsEmpty() {
        fmt.Println("Linked list is empty.")
    } else {
        current := list.head
        for current != nil {
            fmt.Print(current.data, " ")
            current = current.next
        }
        fmt.Println()
    }
}

func (list *DoublyLinkedList) DisplayBackward() {
    if list.IsEmpty() {
        fmt.Println("Linked list is empty.")
    } else {
        current := list.head
        for current.next != nil {
            current = current.next
        }
        for current != nil {
            fmt.Print(current.data, " ")
            current = current.prev
        }
        fmt.Println()
    }
}

// Usage example:
func main() {
    linkedList := &DoublyLinkedList{}
    linkedList.InsertAtHead(5)
    linkedList.InsertAtHead(3)
    linkedList.InsertAtTail(7)
    linkedList.DisplayForward()  // Output: 3 5 7
    linkedList.DisplayBackward()  // Output: 7 5 3
    linkedList.DeleteAtHead()
    linkedList.DeleteAtTail()
    linkedList.DisplayForward()  // Output: 5
}