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
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