求鏈表的倒數第k個節點

思路是使用兩個指針，第一個指針先走k-1步，然後兩個指針一起走，當第一個指針走到結尾的時候，第二個指針指向的就是倒數第K個結點。

class MyNode{
	int value;
	MyNode next;
	
	MyNode(int value){
		this.next = null;
		this.value = value;
	}
}
/**
 * @author David
 * 求鏈表的倒數第k個節點
 */
public class Example4 {

	public static void main(String[] args) {
		//初始化鏈表
			
		MyNode Node1 = new MyNode(1);
		MyNode Node2 = new MyNode(2);
		MyNode Node3 = new MyNode(3);
		MyNode Node4 = new MyNode(4);
		MyNode Node5 = new MyNode(5);
		MyNode Node6 = new MyNode(6);
		MyNode Node7 = new MyNode(7);
		MyNode Node8 = new MyNode(8);
		Node1.next = Node2;
		Node2.next = Node3;
		Node3.next = Node4;
		Node4.next = Node5;
		Node5.next = Node6;
		Node6.next = Node7;
		Node7.next = Node8;
	
		new Example4().fun(Node1, 11);
	}	
	
	private void fun(MyNode first, int k){
		MyNode head = first;
		MyNode tail = first;
		int length = 0;
		while(head!=null){
			head = head.next;
			length++;
		}
		head = first;
		System.out.println(length);
		if(k!=0&&k<length){
			for(int i=0; i<k; i++){
				head = head.next;
			}
			
			while(head!=null){
				head = head.next;
				tail = tail.next;
			}
			System.out.println(tail.value);
		}else{
			System.out.println("input error");
		}
	}

}