0206 Reverse Linked List · cho.sh

0206 Reverse Linked List

Warning

This post is more than a year old. Information may be outdated.

Solved at: 230128 Reverse Linked List

Question

Given the head of a singly linked list, reverse the list, and return the reversed list.

Solution

Backlinks1

Coding Tests

Comments0

No comments yet. Be the first to share your thoughts.

Comments

swift

class Solution {
    func reverseList(_ head: ListNode?) -> ListNode? {
        var itr: ListNode? = head
        guard itr != nil else { return nil }
        var prev : ListNode? = nil // ← this
        while (itr != nil) {
            var next : ListNode? = itr!.next
            itr!.next = prev
            prev = itr
            itr = next
        }
        return prev
    }
}

swift

class Solution {
    func reverseList(_ head: ListNode?) -> ListNode? {
        guard head != nil else { return nil }
        guard head!.next != nil else { return head }
        var next : ListNode? = head!.next
        var reversed : ListNode? = reverseList(next);
        head!.next!.next = head
        head!.next = nil
        return reversed
    }
}

0206 Reverse Linked List

Question

Solution

Improved

Results

Complexity Analysis

Other Answers Online