LeetCode 21. Merge Two Sorted Lists

问题

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

分析

又是一道链表的题目。
归并即可。

代码

# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, x):
#         self.val = x
#         self.next = None

class Solution:
    def mergeTwoLists(self, l1, l2):
        """
        :type l1: ListNode
        :type l2: ListNode
        :rtype: ListNode
        """
        head = ListNode(0)
        l3 = head
        while l1 != None or l2 != None:
            if l1 != None and l2 != None:
                if l1.val < l2.val:
                    l3.next = ListNode(l1.val)
                    l3 = l3.next
                    l1 = l1.next
                else:
                    l3.next = ListNode(l2.val)
                    l3 = l3.next
                    l2 = l2.next
            else:
                while l1 != None:
                    l3.next = ListNode(l1.val)
                    l3 = l3.next
                    l1 = l1.next
                while l2 != None:
                    l3.next = ListNode(l2.val)
                    l3 = l3.next
                    l2 = l2.next
        return head.next