class Solution(object):
def reverseBetween(self, head, left, right):
"""
:type head: ListNode
:type left: int
:type right: int
:rtype: ListNode
"""
right = right -1
left = left -1
while( right-left>=0 ):
print(right-left)
# 左侧节点
l = head
for i in range(left):
l = l.next
# 右侧节点
r = head
for i in range(right):
r = r.next
# print(l.val, r.val)
l.val, r.val = r.val, l.val
right = right-1
left = left+1
print(head)
return head上面的方法其实有那么些问题，更ok的应该是下面这种
class Solution:
def reverseBetween(self, head: ListNode, left: int, right: int) -> ListNode:
# 设置 dummyNode 是这一类问题的一般做法
dummy_node = ListNode(-1)
dummy_node.next = head
pre = dummy_node
for _ in range(left - 1):
pre = pre.next
cur = pre.next
for _ in range(right - left):
next = cur.next
cur.next = next.next
next.next = pre.next
pre.next = next
return dummy_node.next
