CA 15 - Merge Two Linked List

 Merge Two Sorted Lists

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]


CODE:

    Here, we create a temporary linked list and add the merged nodes to the temporary linked list and solve the edge cases by extending the left-out nodes from list1 or list2. using the pointer "ptr" we traverse the temporary linked list.


# 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]:
        temp = ListNode()
        ptr = temp

        while list1 and list2:
            if list1.val < list2.val:
                ptr.next = list1
                list1 = list1.next
            else:
                ptr.next = list2
                list2 = list2.next
           
            ptr = ptr.next

        if list1:
            ptr.next = list1
        elif list2 :
            ptr.next = list2

        return temp.next

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