lintcode 466. 链表节点计数

计算链表中有多少个节点.

样例

给出 1->3->5, 返回 3.

 1 /**
 2  * Definition of ListNode
 3  * class ListNode {
 4  * public:
 5  *     int val;
 6  *     ListNode *next;
 7  *     ListNode(int val) {
 8  *         this->val = val;
 9  *         this->next = NULL;
10  *     }
11  * }
12  */
13 
14 
15 class Solution {
16 public:
17     /*
18      * @param head: the first node of linked list.
19      * @return: An integer
20      */
21     int countNodes(ListNode * head) {
22         // write your code here
23         int count = 0;
24         while (head->next) {
25             count++;
26             head = head->next;
27         }
28         return count;
29     }
30 };