module LinkedList

( LinkedList (..)

, nullNode

, listLength

, appendNode

, insertNode

, deleteNode

, deleteNodeAt

) where

data LinkedList = NULL | LinkedList Integer LinkedList deriving (Eq, Show)

-- | Initialize the head of the linked list

nullNode :: LinkedList

nullNode = NULL

-- | Get the length of the linked list

listLength :: LinkedList -> Integer

listLength NULL = 0

listLength (LinkedList nodeValue nextNode) = listLength nextNode + 1

-- | Append the node with the given value

appendNode :: LinkedList -> Integer -> LinkedList

appendNode NULL insertValue = LinkedList insertValue NULL

appendNode (LinkedList nodeValue nextNode) insertValue

| nextNode == NULL = LinkedList nodeValue (LinkedList insertValue NULL)

| otherwise = LinkedList nodeValue (appendNode nextNode insertValue)

-- | Insert the node at the given position

insertNode :: LinkedList -> Integer -> Integer -> LinkedList

insertNode NULL insertValue _ = LinkedList insertValue NULL

insertNode (LinkedList nodeValue nextNode) insertValue insertPosition

| insertPosition == 0 = LinkedList insertValue (LinkedList nodeValue nextNode)

| otherwise = LinkedList nodeValue (insertNode nextNode insertValue (insertPosition - 1))

-- | Delete the first node with the given value: proceeds from the left to the right

deleteNode :: LinkedList -> Integer -> LinkedList

deleteNode NULL _ = NULL

deleteNode (LinkedList nodeValue nextNode) deleteValue

| nodeValue == deleteValue = nextNode

| otherwise = LinkedList nodeValue (deleteNode nextNode deleteValue)

-- | Delete the node at the given index

deleteNodeAt :: LinkedList -> Integer -> LinkedList

deleteNodeAt NULL _ = NULL

deleteNodeAt (LinkedList nodeValue nextNode) deleteIndex

| deleteIndex == 0 = nextNode

| otherwise = LinkedList nodeValue (deleteNodeAt nextNode (deleteIndex - 1))

main :: IO ()

main = do

let linkedList = nullNode

let linkedList1 = appendNode linkedList 1

let linkedList2 = appendNode linkedList1 2

let linkedList3 = appendNode linkedList2 3

let linkedList4 = appendNode linkedList3 4

let linkedList5 = appendNode linkedList4 5

putStrLn "Empty List"

print linkedList

putStr "\n"

putStrLn "Inserting values..."

print linkedList1

print linkedList2

print linkedList3

print linkedList4

print linkedList5

putStr "\n"

putStrLn "Inserting nodes index 0..."

print (insertNode linkedList1 12 0)

print (insertNode linkedList2 12 0)

print (insertNode linkedList3 12 0)

print (insertNode linkedList4 12 0)

print (insertNode linkedList5 12 0)

putStr "\n"

putStrLn "Inserting nodes index 1..."

print (insertNode linkedList1 12 1)

print (insertNode linkedList2 12 1)

print (insertNode linkedList3 12 1)

print (insertNode linkedList4 12 1)

print (insertNode linkedList5 12 1)

putStr "\n"

putStrLn "Finding out the lengths of the lists..."

print (listLength linkedList1)

print (listLength linkedList2)

print (listLength linkedList3)

print (listLength linkedList4)

print (listLength linkedList5)

putStr "\n"

putStrLn "Deleting nodes..."

print (deleteNode linkedList5 1)

print (deleteNode linkedList5 2)

print (deleteNode linkedList5 3)

print (deleteNode linkedList5 4)

print (deleteNode (deleteNode linkedList5 5) 2)

putStr "\n"

putStrLn "Deleting nodes at the given position..."

print (deleteNodeAt linkedList5 0)

print (deleteNodeAt linkedList5 1)

print (deleteNodeAt linkedList5 2)

print (deleteNodeAt linkedList5 3)

print (deleteNodeAt linkedList5 4)