链表-反转部分单向链表

//反转部分单向链表
public class Node{
    public int value;
    public Node next;
    public Node(int data){
        this.data=data;
    }
}
public Node reversePartLinkedList(Node head,int from,int to){
    int len=0;
    Node node1=null;
    Node fPre=null;
    Node tPos=null;
    while(node!=null){
        len++;
        fPre=len==from-1?node1:fPre;
        tPos=len==to+1?node1:tPos;
        node1=node1.next;
    }
    if(from>to||from<1||to>len){
        return head;
    }
    node1=fPre==null?head:fPre.next;
    Node node2=node1.next;
    node1.next=tPos;
    Node next=null;
    while(node2!=tPos){
        next=node2.next;
        node2.next=node1;
        node1=node2;
        node2=next;
    }
    if(fPre!=null){
        fPre.next=node1;
        return head;
    }
    return node1;
}