算法题，单链表判断是否有环(leetcode easy)，以及判断环入口

“`” 参考回答：

是否有环：

<pre><code>while (faster.next != null && faster.next.next != null) {
faster = faster.next.next;
slower = slower.next;
if (faster == slower) {
return true;
}
}
return false;
</code></pre>

判断环入口：

<pre><code>Node meet = null;
while (faster.next != null && faster.next.next != null) {
faster = faster.next.next;
slower = slower.next;
if (faster == slower) {
meet = faster;
}
}
if (meet != null) {
newSlower = head;
while (newSlower != slower) {
newSlower = newSlower.next;
slower = slower.next;
}
return newSlower;
}
return null;

</code></pre>

<pre><code> "“`