Explore diverse LeetCode solutions in Python, C++, JavaScript, SQL, and TypeScript. Ideal for interview prep, learning, and code practice in multiple programming languages. Github Repo Link
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 * 10 4 ]. 1 <= Node.val <= 1000
Python
# time complexity: O(n) # space complexity: O(1) from typing import Optional class ListNode: def __init__(self, val=0, next=None): self.val = val self.next = next class Solution: def reorderList(self, head: Optional[ListNode]) -> None: if not head: return fast = head slow = head while fast and fast.next: fast = fast.next.next slow = slow.next prev = None curr = slow while curr: curr.next, prev, curr = prev, curr, curr.next first = head second = prev while second.next: first.next, first = second, first.next second.next, second = first, second.next return root = ListNode(1) root.next = ListNode(2) root.next.next = ListNode(3) root.next.next.next = ListNode(4) root.next.next.next.next = ListNode(5) root.next.next.next.next.next = ListNode(6) print(Solution().reorderList(root))
简体中文 
繁體中文 
English 
한국어 
日本語 
Español