LeetCode 369. Plus One Linked List

给一个链表,represents a number such as123;Indicates yes with a linked list1->2->3.Now add one to this number and return the linked list structure;

	public ListNode reverseList(ListNode node) {
    
		if (node.next == null) {
    
			return node;
		}
		ListNode result = reverseList(node.next);
		node.next.next = node;
		node.next = null;
		return result;


	}


	public ListNode plusOne(ListNode head) {
    
		if (head == null) {
    
			return head;
		}
		// 先翻转,In this way, the single digits can be traversed first
		ListNode reverseNode = reverseList(head);

		ListNode cur = reverseNode;
		int mod = 0;
		int add = 1;
		while (cur != null) {
    
			// 遍历每一个节点,
			int sum = cur.val + add + mod;
			cur.val = sum % 10;
			mod = sum / 10;
			add = 0;
			cur = cur.next;
		}
		// There is no rush to splice nodes where the remainder is pure,Anyway, this node is also the first,先翻转链表,Then stitch it together.
		ListNode result = reverseList(reverseNode);
		if (mod != 0) {
    
			ListNode node = new ListNode(1);
			node.next = result;
			return node;

		}
		return result;

	}