LeetCode/24. Swap Nodes in Pairs.py at main · newfull5/LeetCode · GitHub

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# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, val=0, next=None):
#         self.val = val
#         self.next = next
class Solution:
    def swapPairs(self, head: ListNode) -> ListNode:

        if not head:
            return None

        arr1 = []
        arr2 = []

        lists = []

        while True:
            arr1.append(head.val)
            head = head.next
            if head == None:
                break

            arr2.append(head.val)
            head = head.next
            if head == None:
                break

        for i in range(max(len(arr1),len(arr2))):
            try:
                lists.append(arr2[i])
                lists.append(arr1[i])
            except IndexError:
                lists.append(arr1[i])

        answer = ListNode(lists.pop())

        while lists:
            answer = ListNode(lists.pop(), answer)

        return answer