merge-two-sorted-lists.py

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

# Time: O(n), n is the length of shorter linked-list
# Space: O(n), n is the length of longer linked-list
class Solution(object):
    def mergeTwoLists(self, l1, l2):
        """
        :type l1: ListNode
        :type l2: ListNode
        :rtype: ListNode
        """
        dummy = ListNode(0)
        p = dummy
        while l1 is not None and l2 is not None:
            if l1.val < l2.val:
                p.next = l1
                l1 = l1.next
            else:
                p.next = l2
                l2 = l2.next
            p = p.next
        if l1 is not None:
            p.next = l1
        if l2 is not None:
            p.next = l2
        return dummy.next