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class LNode:
def __init__(self):
self.data = None # 数据域
self.next = None # 指针域
# 方法功能: 对单链表进行逆序 输入参数: head: 链表头结点
# 方法1: 就地逆序
def Reverse1(head):
# 判断链表是否为空
if head == None or head.next == None:
return
pre = None # 前驱结点
cur = None # 当前结点
next = None # 后继结点
# 把链表首结点变为尾节点
cur = head.next
next = cur.next
cur.next = None
pre = cur
cur = next
# 是当前遍历到的结点cur 指向其前驱结点
while cur.next != None:
next = cur.next
cur.next = pre
pre = cur
cur = next
# 链表的头结点指向倒数第二个结点
cur.next = pre
head.next = cur
# 方法二:插入法
def Reverse2(head):
# 判断链表是否为空
if head is None or head.next is None:
return
cur = None
next = None
cur = head.next.next
# 设置链表第一个结点为尾结点
head.next.next = None
# 遍历到结点插入到头结点的后面
while cur is not None:
next = cur.next
cur.next = head.next
head.next = cur
cur = next
if __name__ == '__main__':
i = 1
# 链表头结点
head = LNode()
cur = head
# 构造单链表
while i < 8:
tmp = LNode()
tmp.data = i
cur.next = tmp
cur = tmp
i += 1
print('逆序前:')
cur = head.next
while cur != None:
print(cur.data)
cur = cur.next
print('逆序后 Reverse1 :')
Reverse1(head)
cur = head.next
while cur != None:
print(cur.data)
cur = cur.next
print('逆序后 Reverse2 :')
Reverse2(head)
cur = head.next
while cur != None:
print(cur.data)
cur = cur.next
输出结果如下:
逆序前:
1
2
3
4
5
6
7
逆序后 Reverse1 :
7
6
5
4
3
2
1
逆序后 Reverse2 :
1
2
3
4
5
6
7