92. 反转链表 II

原题

https://leetcode.cn/problems/reverse-linked-list-ii/description/

思路

双指针

复杂度

时间：O(n)
空间：O(1)

Python代码

# Definition for singly-linked list.
# class ListNode(object):
#     def __init__(self, val=0, next=None):
#         self.val = val
#         self.next = next
class Solution(object):
    def reverseBetween(self, head, left, right):
        """
        :type head: Optional[ListNode]
        :type left: int
        :type right: int
        :rtype: Optional[ListNode]
        """
        dummy = pre = ListNode(0, head)
        for i in range(left - 1):
            pre = pre.next 
        cur = pre.next
        for j in range(left, right):
            temp = cur.next 
            cur.next = temp.next 
            temp.next = pre.next
            pre.next = temp
        return dummy.next

Go代码

/**
 * Definition for singly-linked list.
 * type ListNode struct {
 *     Val int
 *     Next *ListNode
 * }
 */
func reverseBetween(head *ListNode, left int, right int) *ListNode {
	dummy := &ListNode{0, head}
	pre := dummy
	for i := 0; i < left-1; i++ {
		pre = pre.Next
	}
	cur := pre.Next
	for j := left; j < right; j++ {
		temp := cur.Next
		cur.Next = temp.Next
		temp.Next = pre.Next
		pre.Next = temp
	}
	return dummy.Next
}