链表----两个链表相加生成相加链表

关键点：

• 1、将链表拆成左右两部分
• 2、合并左右两部分 

//1、将链表从中间断开，分成左右两部分
	public static Node reCombination(Node head) {
		if(head == null || head.next == null || head.next.next == null) {
			return head;
		}
		//找中点从中间断开
		Node p1 = head.next.next;
		Node p2 = head.next;
		while(p1.next != null && p1.next.next != null) {
			p1 = p1.next.next;
			p2 = p2.next;
		}//p2到达中点位置
		Node right = p2.next;//右半部分链表头
		p2.next = null;//断开
		printList(head);
		printList(right);
		return mergeList(head,right);	
	}
	
	//2、合并左右两部分
	public static Node mergeList(Node left,Node right) {
		if(left == null || right == null)  return null;
		Node head = left;
		Node nextL = null;
		Node nextR = null;
		while(left.next != null) {
			nextL = left.next;
			left.next = right;
			nextR = right.next;
			left = nextL;
			right.next = left;
			right = nextR;
		}
		if(left != null) {
			left.next = right;
		}
		
		return head;	
	}