【Leetcode】21. Merge Two Sorted Lists

Description

https://leetcode.com/problems/merge-two-sorted-lists/

Merge two sorted linked lists and return it as a new list. The new list should be made by splicing together the nodes of the first two lists.

Example:

Input: 1->2->4, 1->3->4
Output: 1->1->2->3->4->4

Solution

# Definition for singly-linked list.
# class ListNode
#     attr_accessor :val, :next
#     def initialize(val)
#         @val = val
#         @next = nil
#     end
# end

# @param {ListNode} l1
# @param {ListNode} l2
# @return {ListNode}
def merge_two_lists(l1, l2)
    head = ListNode.new(nil)
    current_node = head

    while !l1.nil? && !l2.nil? do
        if l1.val <= l2.val
            current_node.next = l1
            l1 = l1.next
        else
            current_node.next = l2
            l2 = l2.next
        end
        current_node = current_node.next
    end

    if !l1.nil?
        current_node.next = l1
    end

    if !l2.nil?
        current_node.next = l2
    end

    head.next
end