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466. Count Linked List Nodes【Naive】

Count how many nodes in a linked list.

Example

Given 1->3->5, return 3.

 

解法一：

 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         if (head == NULL) {
23             return 0;
24         } else if (head->next == NULL) {
25             return 1;
26         }
27         
28         return 1 + countNodes(head->next);
29     }
30 };

递归

 

解法二：

 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         if (head == NULL) {
23             return 0;
24         } 
25         
26         int sum = 0;
27         while (head != NULL) {
28             ++sum;
29             head = head->next;
30         }
31         
32         return sum;
33     }
34 };

 

 

posted on 2018-02-03 15:31  LastBattle  阅读(170)  评论(0)  编辑  收藏  举报