# Merge Two Sorted [[linked-list|Lists]] https://leetcode.com/problems/merge-two-sorted-lists/ - User `prehead` to initiate the iteration - Utilize the fact that when one list is duplicated, the other list can be immediately appended. ```python # class ListNode: # def __init__(self, val=0, next=None): # self.val = val # self.next = next prehead = ListNode(-1) prev = prehead while list1 and list2: if list1.val <= list2.val: prev.next = list1 list1 = list1.next else: prev.next = list2 list2 = list2.next prev = prev.next prev.next = list1 if list1 else list2 return prehead.next ```