21 - Merge Two Sorted Lists

2020/03/25

leetcode

Problem

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

Notes

Recursion is your friend!

Solution

Solution 1: Recursive

class Solution:
    def mergeTwoLists(self, l1, l2):
        if not l1:
            return l2
        if not l2:
            return l1

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

TODO Solution 2: How to do it none recursively