链表之单向链表（python）

链表中最简单的一种是单向链表，它包含两个域，一个信息域和一个指针域。这个链接指向列表中的下一个节点，而最后一个节点则指向一个空值。

python代码实现：

# 链表中的节点的数据结构
class ListNode(object):
    def __init__(self, x):
        self.val = x
        self.next = None

# 实例化
A = ListNode('a')
B = ListNode('b')
C = ListNode('c')
A.next = B
B.next = C

# 这样，一条链表就形成了。
# 'a' -> 'b' -> 'c'

# 遍历链表
tmp = A
while tmp != None:
    print(tmp.val)
    tmp = tmp.next

# 递归遍历链表
def listorder(head):
    if head:
        print(head.val)
        listorder(head.next)

listorder(A)

翻转一条单向链表：

需求：

Input: 1->2->3->4->5->NULL
Output: 5->4->3->2->1->NULL

class ListNode(object):
    def __init__(self, x):
        self.val = x
        self.next = None

class Solution(object):
    def reverseList(self, head):
        """
        :type head: ListNode
        :rtype: ListNode
        """
        dummy = head
        tmp = dummy

        while head and head.next != None:
            dummy = head.next
            head.next = dummy.next
            dummy.next = tmp
            tmp = dummy
        return dummy

head = ListNode(1)
head.next = ListNode(2)
head.next.next = ListNode(3)
head.next.next.next = ListNode(4)
head.next.next.next.next = ListNode(5)

solution = Solution()
reverse_head = solution.reverseList(head)
tmp = reverse_head
while tmp:
    print(tmp.val)
    tmp = tmp.next