Top-Interview-Questions-LeetCode/Remove-Duplicates.py at main · PRAN20/Top-Interview-Questions-LeetCode · GitHub

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class Solution:
    def deleteDuplicates(self, head: ListNode) -> ListNode:
        # sentinel
        sentinel = ListNode(0, head)

        # predecessor = the last node
        # before the sublist of duplicates
        pred = sentinel

        while head:
            # if it's a beginning of duplicates sublist
            # skip all duplicates
            if head.next and head.val == head.next.val:
                # move till the end of duplicates sublist
                while head.next and head.val == head.next.val:
                    head = head.next
                # skip all duplicates
                pred.next = head.next
            # otherwise, move predecessor
            else:
                pred = pred.next

            # move forward
            head = head.next

        return sentinel.next