数据结构与算法（二）——链表中环的检测

public class Demo {
 
	public static void main(String[] args) {
		// 链表中环的检测
		Node node = getNode(10, true);
		boolean checkRing = checkRing(node);
		System.out.println(checkRing);
	}
 
	// 环检测
	private static boolean checkRing(Node node) {
		Node fast = node;
		Node show = node;
		while (fast != null && fast.next != null) {
			fast = fast.next.next;
			show = show.next;
			if (fast == show) {
				return true;
			}
		}
		return false;
	}
 
	// 获取普通链表
	private static Node getNode(Integer n, boolean ring) {
		Node head = null;
		Node node = null;
		for (int i = 1; i <= n; i++) {
			Node next = new Node(i);
			if (node == null) {
				node = next;
				head = next;
			} else {
				node.next = next;
				node = next;
			}
		}
		// 是否造环
		if (ring) {
			node.next = head;
		}
		return head;
	}
 
	static class Node {
		public Node next;
		public Integer value;
 
		public Node(Integer value) {
			this.value = value;
		}
	}
}