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）：

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

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

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

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！