92. 反转链表 II

package main
import "fmt"
type ListNode struct {
         Val int
         Next *ListNode
}
func reverseBetween1(head *ListNode, m int, n int) *ListNode {
    dummyNode := &ListNode{}
    dummyNode.Next = head
    begin := dummyNode
    for i:=0;i<m-1;i++{
        begin = begin.Next
    }
    var pre *ListNode
    curr := begin.Next
    for i:=0;i<n-m+1;i++{
        tmp := curr.Next
        curr.Next = pre
        pre = curr
        curr = tmp
    }
    begin.Next.Next = curr// 链接后节点
    begin.Next = pre // 开始反转的最后节点
    return dummyNode.Next
}
func reverseBetween(head *ListNode, m int, n int) *ListNode {
    dummyHead :=&ListNode{
        Val:  -1,
        Next: head,
    }
    curr :=head
    i := 1
    pre :=dummyHead
    var next *ListNode
    var start *ListNode
    for curr!=nil{
        if i==m {
            start = curr
        }
        if i==n{
            next = curr.Next
            curr.Next = nil
            pre.Next = revertNode(start)
            start.Next = next
            return dummyHead.Next
        }
        if i<=m-1{
            pre = curr //获取前一个节点
        }
        curr = curr.Next
        i++
    }
    return dummyHead.Next
}
func revertNode(head*ListNode)*ListNode{
    curr :=head
    var pre *ListNode
    for curr!=nil{
        pre,curr,curr.Next = curr,curr.Next,pre
    }
    return pre
}
func revertNode1(head*ListNode)*ListNode{
      var pre *ListNode
      curr := head
      for curr!=nil{
          tmp :=curr.Next
          curr.Next = pre
          pre = curr
            curr= tmp
      }
    return pre
}
func makeLinkedList(list []int)*ListNode{
    dummyNode := &ListNode{} // 创建哑结点 指向头节点
    curr := dummyNode
    for i:=0;i<len(list);i++{
        curr.Next= &ListNode{Val:list[i]}
        curr = curr.Next
    }
    return dummyNode.Next
}
func main() {
     head := makeLinkedList([]int{1,2,3,4,5})
    // head = revertNode(head)
     head = reverseBetween(head,1,2)
     for head!=nil{
         fmt.Println(head.Val)
         head = head.Next
     }
}