【LeetCode with Python】 Reorder List

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原题页面：https://oj.leetcode.com/problems/reorder-list/

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Given a singly linked list L: L0→L1→…→Ln-1→Ln,

reorder it to: L0→Ln→L1→Ln-1→L2→Ln-2→…

You must do this in-place without altering the nodes' values.

For example,

Given

{1,2,3,4}

, reorder it to

{1,4,2,3}

.

class Solution:

    # @param head, a ListNode
    # @return nothing
    def reorderList(self, head):

        if None == head:
            return
        cur = head
        count = 0
        while None != cur:
            cur = cur.next
            count += 1
        if count <= 2:
            return

        half_count = (count - 1) / 2
        cur2 = head
        for i in range(0, half_count):
            cur2= cur2.next
        cur2_next = cur2.next
        cur2.next = None
        cur2 = reverse_list(cur2_next, None, None)

        cur1 = head
        time_count = int(count / 2)
        for i in range(0, time_count):
            cur2_next = cur2.next
            cur2.next = cur1.next
            cur1.next = cur2
            cur1 = cur2.next
            cur2 = cur2_next