147-21. 合并两个有序链表

将两个升序链表合并为一个新的 升序 链表并返回。新链表是通过拼接给定的两个链表的所有节点组成的。(我写的第一个)
class Solution(object):
    def mergeTwoLists1(self, l1, l2):
        """我的思路是,既然要合并,直接遍历出来,排序重构
        :type l1: ListNode
        :type l2: ListNode
        :rtype: ListNode
        """
        temp_list = []
        if l1:
            self.search(l1, temp_list)
        if l2:
            self.search(l2, temp_list)
        temp_list = sorted(temp_list, reverse=True)
        pre = None
        for i in temp_list:
            cur = ListNode(i)
            cur.next = pre
            pre = cur
        return pre

    def search(self, n1, temp_list):
        temp = n1
        temp_list.append(temp.val)
        while temp.next:
            temp = temp.next
            temp_list.append(temp.val)

    def mergeTwoLists(self, l1, l2):
        """这个我的好,内存消耗小,同时执行效率高
        :type l1: ListNode
        :type l2: ListNode
        :rtype: ListNode
        """
        head = ListNode(0)
        a = head
        while l1 and l2:
            if l1.val < l2.val:
                a.next = l1
                l1 = l1.next
            else:
                a.next = l2
                l2 = l2.next
            a = a.next
        else:
            if l1:
                a.next = l1
            else:
                a.next = l2
        return head.next


if __name__ == '__main__':
    root1 = ListNode(1)
    n2 = ListNode(2)
    n3 = ListNode(4)
    n2.next = n3
    root1.next = n2

    root2 = ListNode(1)
    n4 = ListNode(3)
    n5 = ListNode(4)
    n4.next = n5
    root2.next = n4

    s1 = Solution()
    new_root = s1.mergeTwoLists(root1, root2)
    new_root.search()