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21. Merge Two Sorted Lists

Linked List Recursion

Problem - Merge Two Sorted Lists

Easy

You are given the heads of two sorted linked lists list1 and list2.

Merge the two lists into one sorted list. The list should be made by splicing together the nodes of the first two lists.

Return the head of the merged linked list.

 

Example 1:

Input: list1 = [1,2,4], list2 = [1,3,4]
Output: [1,1,2,3,4,4]

Example 2:

Input: list1 = [], list2 = []
Output: []

Example 3:

Input: list1 = [], list2 = [0]
Output: [0]

 

Constraints:

  • The number of nodes in both lists is in the range [0, 50].
  • -100 <= Node.val <= 100
  • Both list1 and list2 are sorted in non-decreasing order.

Solutions

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# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, val=0, next=None):
#         self.val = val
#         self.next = next
class Solution:
    def mergeTwoLists(self, list1: Optional[ListNode], list2: Optional[ListNode]) -> Optional[ListNode]:
        list1_n = list1
        list2_n = list2
        result = pointer = ListNode()

        while list1_n and list2_n:
            if list1_n.val < list2_n.val:
                result.next = list1_n
                list1_n = list1_n.next
            else:
                result.next = list2_n
                list2_n = list2_n.next
            result = result.next

        result.next = list1_n if list1_n else list2_n

        return pointer.next

Submission Stats:

  • Runtime: 0 ms (100.00%)
  • Memory: 17.8 MB (61.55%)