Merge Two Sorted Lists

题目描述

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.

解题方法

这一题是很多题目的基础，所以要熟练掌握

Solution

class Solution(object):
    def mergeTwoLists(self, l1, l2):
        """
        :type l1: ListNode
        :type l2: ListNode
        :rtype: ListNode
        """
        if not l1:
            return l2
        if not l2:
            return l1

        dummy = ListNode(0)
        head = dummy
        while l1 and l2:
            if l1.val < l2.val:
                head.next = l1
                head = head.next
                l1 = l1.next
            else:
                head.next = l2
                head = head.next
                l2 = l2.next

        # 注意这里是if，直接将后面的连上
        if l1:
            head.next = l1

        if l2:
            head.next = l2

        return dummy.next

Reference