Swapping Pairs In A Linked List In Python, One Link Disappears?

I have been learning about linked lists, and implementing one in python has been easier than I expected. However, when it has come to solving the problem of 'swapping pairs in a li

Solution 1:

Your swapPairsI function is returning the new head of your linked list. You need to update it accordingly:

thisLList.head = thisLList.swapPairsI(thisLList.head)

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Or better yet, you should change your swapPairsI function so that it doesn't have to take a node as parameter:

defswapPairsI(self): # iterative
    prev = Node(0)
    prev.next = self.head
    temp = prev

    while temp.nextand temp.next.next:
        ptrOne = temp.next
        ptrTwo = temp.next.next# change the pointers to the swapped pointers
        temp.next = ptrTwo
        ptrOne.next = ptrTwo.next
        ptrTwo.next = ptrOne
        temp = temp.next.nextself.head = prev.next

In which case, you can simply call:

thisLList.swapPairsI()