143. Reorder List
You are given the head of a singly linked-list. The list can be represented as:
L0 → L1 → … → Ln - 1 → Ln
Reorder the list to be on the following form:
L0 → Ln → L1 → Ln - 1 → L2 → Ln - 2 → …
You may not modify the values in the list's nodes. Only nodes themselves may be changed.
Example 1:
Input: head = [1,2,3,4] Output: [1,4,2,3]
Example 2:
Input: head = [1,2,3,4,5] Output: [1,5,2,4,3]
Constraints:
- The number of nodes in the list is in the range
[1, 5 * 104]. 1 <= Node.val <= 1000
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1# Definition for singly-linked list.
2# class ListNode:
3# def __init__(self, val=0, next=None):
4# self.val = val
5# self.next = next
6class Solution:
7 def reorderList(self, head: Optional[ListNode]) -> None:
8 """
9 Do not return anything, modify head in-place instead.
10 """
11
Starter codePython 3Spaces: 4
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1# Definition for singly-linked list.
2# class ListNode:
3# def __init__(self, val=0, next=None):
4# self.val = val
5# self.next = next
6class Solution:
7 def reorderList(self, head: Optional[ListNode]) -> None:
8 """
9 Do not return anything, modify head in-place instead.
10 """
11
Starter codePython 3Spaces: 4
Examples
Input
[1,2,3,4]
Input
[1,2,3,4,5]
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