链表笔记

package  test;
public class ListNode{
	int val;
	ListNode next;
	public ListNode(int x) {
		val = x;
	}
	
	public ListNode() {}
	
	
	public static void main(String[] args) {
		int n = 2;
		ListNode l1 = new ListNode(1);
		ListNode l2 = new ListNode(2);
		ListNode l3 = new ListNode(3);
		ListNode l4 = new ListNode(4);
		ListNode l5 = new ListNode(5);
		ListNode head = l1;
		l1.next = l2;
		l2.next = l3;
		l3.next = l4;
		l4.next = l5;
		while(head != null) {
			System.out.println(head.val);
			head = head.next;
		}
		
		ListNode h1 = new ListNode();
		h1.next = head; //这里将 h1 指向了 head
　　　　　　　　　 ListNode first = h1; // 对 first 操作的时候， h1 和 head 也在改变。在内存三者共用同一块内存
		first.next = l3;
		
		while(h1 !=  null) {
			System.out.println(h1.val);
			h1 = h1.next;
		}
		while(head != null) {
			System.out.println(head.val);
			head = head.next;
		}
		
	}
	
}