Leetcode – Linked List Cycle
Given a linked list, determine if it has a cycle in it.
Analysis
If we have 2 pointers  fast and slow. It is guaranteed that the fast one will meet the slow one if there exists a circle.
The problem can be demonstrated in the following diagram:
Java Solution
public class Solution { public boolean hasCycle(ListNode head) { ListNode fast = head; ListNode slow = head; while(fast != null && fast.next != null){ slow = slow.next; fast = fast.next.next; if(slow == fast) return true; } return false; } } 
<pre><code> String foo = "bar"; </code></pre>

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