面試題16：翻轉鏈表

題目：定義一個函數,輸入一個鏈表的頭結點,反轉鏈表並輸出反轉後的鏈表頭結點

思路：三個指針,pre指向已經完成的鏈表頭結點,middle指向要操作的結點,next指向沒操作的節點

public class ReverseList {

	public static Node reverseList(Node head){
		if(head==null)
			return null;
		else if(head.getNext()==null)
			return head;
		else{
			Node pre = null;
			Node middle = head;
			Node next = head.getNext();
			while(next!=null){
				middle.setNext(pre);
				pre = middle;
				middle = next;
				next = next.getNext();
			}
			middle.setNext(pre);
			return middle;
		}
	}
}
class Node{
	private Integer data;
	private Node next;
	public Integer getData() {
		return data;
	}
	public void setData(Integer data) {
		this.data = data;
	}
	public Node getNext() {
		return next;
	}
	public void setNext(Node next) {
		this.next = next;
	}
	public Node() {
		super();
	}
	public Node(Integer data) {
		this.data = data;
		next = null;
	}
	@Override
	public String toString() {
		return "Node [data=" + data + "]";
	}	
}