206. Reverse Linked List

Reverse a singly linked list.

Example:

Input: 1->2->3->4->5->NULL
Output: 5->4->3->2->1->NULL

Follow up:

A linked list can be reversed either iteratively or recursively. Could you implement both?

# @lc code=start
using LeetCode

reverse_list(head::Nothing) = head
function reverse_list(head::ListNode)::ListNode
    new_head = pre_node = nothing
    while !isnothing(head)
        new_head = ListNode(head.val)
        pre_node, new_head.next = new_head, pre_node
        head = head.next
    end
    return new_head
end
# @lc code=end

reverse_list (generic function with 2 methods)

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