反转链表

反转整个链表

/**
 * Definition for singly-linked list.
 * type ListNode struct {
 *     Val int
 *     Next *ListNode
 * }
 */
func reverseList(head *ListNode) *ListNode {
    if head==nil||head.Next==nil{
        return head
    }
    last:=reverseList(head.Next)
    head.Next.Next=head
    head.Next=nil
    return last
}

　反转链表前N个节点

//反转前n个节点
func reverseN(head *ListNode, n int) *ListNode{
    if n==1{
        end = head.Next
        return head
    }
    last := reverseN(head.Next,n-1)
    head.Next.Next=head
    head.Next=end
    return last
}

　反转链表在区间（left，right）之间的节点

/**
 * Definition for singly-linked list.
 * type ListNode struct {
 *     Val int
 *     Next *ListNode
 * }
 */
func reverseBetween(head *ListNode, left int, right int) *ListNode {
     if left == 1{
         return reverseN(head, right)
     }
     head.Next = reverseBetween(head.Next,left-1,right-1)
     return head
}
var end *ListNode = nil

//反转前n个节点
func reverseN(head *ListNode, n int) *ListNode{
    if n==1{
        end = head.Next
        return head
    }
    last := reverseN(head.Next,n-1)
    head.Next.Next=head
    head.Next=end
    return last
}