21. Merge Two Sorted Lists

문제

Merge two sorted linked lists and return it as a new list. The new list should be made by splicing together the nodes of the first two lists.

Example:

Input: 1->2->4, 1->3->4
Output: 1->1->2->3->4->4

풀이

Divide & Conquer 전략에 따라 작은 문제를 해결하고, 이를 조합하여 큰 문제를 해결한다.

class Solution:
    def mergeTwoLists(self, l1: ListNode, l2: ListNode) -> ListNode:
        if l1 is None :
            return l2

        if l2 is None :
            return l1

        if (l1.val > l2.val) :
            head = ListNode(l2.val)
            head.next = self.mergeTwoLists(l1, l2.next)
        else :
            head = ListNode(l1.val)
            head.next = self.mergeTwoLists(l1.next, l2)

        return head