当前位置： 面试刷题>> 链表节点计数 (经典算法题500道)
### 题目描述
给定一个单向链表的头节点 `head`，请编写一个函数来计算该链表中节点的总数。链表节点的定义如下（以Python为例，但PHP和JavaScript有类似的定义方式）：
```python
class ListNode:
def __init__(self, val=0, next=None):
self.val = val
self.next = next
```
### 函数签名
对于不同的编程语言，函数签名可能略有不同，但基本思路一致：
- **Python**: `def countNodes(head: ListNode) -> int`
- **PHP**: `function countNodes($head) { ... }`，其中`$head`是链表头节点的引用
- **JavaScript**: `function countNodes(head) { ... }`，其中`head`是链表头节点的引用
### 示例代码
#### Python 示例
```python
class ListNode:
def __init__(self, val=0, next=None):
self.val = val
self.next = next
def countNodes(head: ListNode) -> int:
count = 0
current = head
while current:
count += 1
current = current.next
return count
# 示例使用
node1 = ListNode(1)
node2 = ListNode(2)
node3 = ListNode(3)
node1.next = node2
node2.next = node3
print(countNodes(node1)) # 输出: 3
```
#### PHP 示例
```php
class ListNode {
public $val = 0;
public $next = null;
function __construct($val = 0, $next = null) {
$this->val = $val;
$this->next = $next;
}
}
function countNodes($head) {
$count = 0;
$current = $head;
while ($current !== null) {
$count++;
$current = $current->next;
}
return $count;
}
// 示例使用
$node1 = new ListNode(1);
$node2 = new ListNode(2);
$node3 = new ListNode(3);
$node1->next = $node2;
$node2->next = $node3;
echo countNodes($node1); // 输出: 3
```
#### JavaScript 示例
```javascript
class ListNode {
constructor(val = 0, next = null) {
this.val = val;
this.next = next;
}
}
function countNodes(head) {
let count = 0;
let current = head;
while (current !== null) {
count++;
current = current.next;
}
return count;
}
// 示例使用
const node1 = new ListNode(1);
const node2 = new ListNode(2);
const node3 = new ListNode(3);
node1.next = node2;
node2.next = node3;
console.log(countNodes(node1)); // 输出: 3
```
### 码小课网站内容分享
码小课网站中包含了更多关于链表操作的详细教程和练习题，包括但不限于链表节点的插入、删除、反转、查找以及排序等算法。通过学习这些内容，你可以更加深入地理解链表这一数据结构，并掌握解决链表相关问题的技巧。欢迎大家访问码小课网站，共同学习进步！