466. Count Linked List Nodes【Naive】

Count how many nodes in a linked list.

Example

Given 1->3->5, return 3.

解法一：

 /**
  * Definition of ListNode
  * 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) {
         if (head == NULL) {
             return ;
         } else if (head->next == NULL) {
             return ;
         }

         return  + countNodes(head->next);
     }
 };

递归

解法二：

 /**
  * Definition of ListNode
  * 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) {
         if (head == NULL) {
             return ;
         } 

         int sum = ;
         while (head != NULL) {
             ++sum;
             head = head->next;
         }

         return sum;
     }
 };