Solution in Ruby 021

solution/021.Merge Two Sorted Lists/Solution.rb

@@ -0,0 +1,39 @@
+# 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)
+  return l1 if l2.nil?
+  return l2 if l1.nil?
+
+  head = ListNode.new(0)
+  temp = head
+
+  until l1.nil? && l2.nil?
+    if l1.nil?
+      head.next = l2
+      break
+    elsif l2.nil?
+      head.next = l1
+      break
+    elsif l1.val < l2.val
+      head.next = ListNode.new(l1.val)
+      head = head.next
+      l1 = l1.next
+    else
+      head.next = ListNode.new(l2.val)
+      head = head.next
+      l2 = l2.next
+    end
+  end
+  temp.next
+end
+