LeetCode#21. Merge Two Sorted Li

easy难度，将两个已排序链表合并成一个

class Solution(object):
    def mergeTwoLists(self, l1, l2):
        """
        :type l1: ListNode
        :type l2: ListNode
        :rtype: ListNode
        """
        if  l1:
            return l2
        elif l2:
            return l1
        p1,p2 = l1,l2
        result = ListNode(0)
        q = result
        while (p1 and p2):
            if p1.val<=p2.val:
                temp = ListNode(p1.val)
                q.next = temp
                p1 = p1.next
            else:
                temp = ListNode(p2.val)
                q.next = temp
                p2 = p2.next
            q = q.next
        if p1:
            q.next = p1
        elif p2:
            q.next = p2
        return result.next

我用的最直接的方法，看到了一个五行的递归

class Solution(object):
    def mergeTwoLists(self, l1, l2):
        if l1 and l2:
            if l1.val >l2:
                l1,l2 = l2,l1
            l1.next = mergeTwoList(l1.next,l2)
        return l1 or l2