DLList InsertAtP

InsertAtP.go

func InsertAtP(head **DLNode, p int, x int) {
	if p < 1 {
		fmt.Println("Positions start at 1. Invalid Position.")
		return
	}

	if p == 1 {
		InsertAtStart(head, x)
		return
	}
	if *head == nil {
		fmt.Println("Position Invalid.")
		return
	}
	current := *head
	i := 1
	// Find the penultimate node
	for i < p-1 && current.Next != nil {
		current = current.Next
		i++
	}
	// This means we reached the end of the list and i != p-1
	if i < p-1 {
		fmt.Println("Invalid Position")
		return
	}
	tmp := &DLNode{Data: x}
	fmt.Println("Inserting", tmp, "at position", p)
	tmp.Prev = current
	tmp.Next = current.Next
	if current.Next != nil {
		current.Next.Prev = tmp
	}
	current.Next = tmp
}