Swap-Nodes-InPairs

class ListNode:
    def __init__(self, val=0):
        self.val = val
        self.next = None


# Function to swap nodes in pairs
def swapPairs(head):
    
    dummy = ListNode(0)
    dummy.next = head
    prev = dummy
    
    while prev.next and prev.next.next:
        
        first = prev.next
        second = prev.next.next
        
        # Swapping
        first.next = second.next
        second.next = first
        prev.next = second
        
        # Move pointer forward
        prev = first
    
    return dummy.next


# Helper function to create linked list
def createList(arr):
    if not arr:
        return None
    
    head = ListNode(arr[0])
    current = head
    
    for val in arr[1:]:
        current.next = ListNode(val)
        current = current.next
    
    return head


# Helper function to print linked list
def printList(head):
    result = []
    while head:
        result.append(head.val)
        head = head.next
    print(result)


# User Input
arr = list(map(int, input("Enter linked list elements: ").split()))

head = createList(arr)
new_head = swapPairs(head)

print("After swapping:")
printList(new_head)