快慢指针解决单向链表是否有环的一系列问题

talk is cheap,show me the code......

证明参考：https://www.cnblogs.com/zhuzhenwei918/p/7491892.html
package singleLinkedList;

/**
* @author Leon
* @date 创建时间：2017年10月15日 下午6:13:40
* @version 1.0
* 类说明 :
* 单向链表相关问题 例如：1 - 2 - 3 - 4 - 5 - 6 - 4 - .....
* 1、是否有环
* 2、环的长度
* 3、带环链表的实际长度
*/
public class Test
{
public static void main(String[] args)
{
Node n1 = new Node(1);
Node n2 = new Node(2);
Node n3 = new Node(3);
Node n4 = new Node(4);
Node n5 = new Node(5);
Node n6 = new Node(6);

n1.next = n2;
n2.next = n3;
n3.next = n4;
n4.next = n5;
n5.next = n6;
n6.next = n4;

System.out.println(isHoop(n1));
System.out.println(getLengthOfHoop(n1));
System.out.println(getLengthOfList(n1));
}

/*
* 对于问题1，使用追赶的方法，设定两个指针slow、fast，从头指针开始，每次分别前进1步、2步。
* 如存在环，则两者相遇；如不存在环，fast遇到NULL退出
*/
private static String isHoop(Node n1)
{
Node slow, fast;
slow = n1;
fast = n1;
while (fast != null)
{
fast = fast.next.next;
slow = slow.next;
if (fast == slow)
{
return "链表有环哦~";
}
}

return "链表没环哦~";
}

/*
* 对于问题2，记录下问题1的碰撞点p，slow、fast从该点开始，再次碰撞所走过的操作数就是环的长度s。
*/
private static String getLengthOfHoop(Node n1)
{
Node slow, fast, p = null;
slow = n1;
fast = n1;
while (fast != null)
{
fast = fast.next.next;
slow = slow.next;
if (fast == slow)
{
p = fast;
//System.out.println(p.value);
break;
}
}
if (p == null)
{

return "链表没环";
}

slow = p.next;
fast = p.next.next;
int operation = 1;
while (slow.value != fast.value)
{
s
4000
low = slow.next;
fast = fast.next.next;
operation++;
}
return "环的长度是："+String.valueOf(operation);
}

/*
* 对于问题3,和前半部分加在一起就可以了。
*/
private static String getLengthOfList(Node n1)
{
Node slow, fast, p = null;
slow = n1;
fast = n1;
while (fast != null)
{
fast = fast.next.next;
slow = slow.next;
if (fast == slow)
{
p = fast;
//System.out.println(p.value);
break;
}
}
if (p == null)
{
return "链表没环";
}

slow=n1;
int result=0;
while(slow.value!=p.value)
{
result++;
slow=slow.next;
//System.out.println("hello");
}
//System.out.println(result);
//System.out.println(getLengthOfHoop(n1).charAt(getLengthOfHoop(n1).length()-1));
int resultT = result+Character.getNumericValue(getLengthOfHoop(n1).charAt(getLengthOfHoop(n1).length()-1));
//System.out.println(resultT);
return "链表长度："+resultT;
}
}

class Node
{
public int value;
public Node next = null;

public Node(int value)
{
super();
this.value = value;
}
}