Merge Two Sorted Lists.py

# https://leetcode.com/problems/merge-two-sorted-lists/
# Hak Soo Kim
# 2/1/2022

# Definition for singly-linked list.
# class ListNode(object):
#     def __init__(self, val=0, next=None):
#         self.val = val
#         self.next = next
class Solution(object):
    def mergeTwoLists(self, list1, list2):
        if (list1 == None):
            return list2
        elif (list2 == None):
            return list1
        elif (list1.val < list2.val):
            list1.next = self.mergeTwoLists(list1.next, list2)
            return list1
        else:
            list2.next = self.mergeTwoLists(list1, list2.next)
            return list2

        """
        :type list1: Optional[ListNode]
        :type list2: Optional[ListNode]
        :rtype: Optional[ListNode]
        """

# You are given the heads of two sorted linked lists list1 and list2.
#
# Merge the two lists in a 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.