链表节点计数-LintCode

计算链表中有多少个节点.

样例：
给出 1->3->5, 返回 3.

#ifndef C466_H#define C466_H#include<iostream>using namespace std;/** Count how many nodes in a linked list.* * Example* Given 1->3->5, return 3.*/class ListNode{public:    int val;    ListNode *next;    ListNode(int val){        this->val = val;        this->next = NULL;    }};class Solution {public:    /*    * @param head: the first node of linked list.    * @return: An integer    */    int countNodes(ListNode * head) {        // write your code here        if (head == NULL)            return 0;        ListNode *p = head;        int len = 0;        while (p != NULL)        {            len++;            p = p->next;        }        return len;    }};#endif