以下是在C++中逆轉單鏈表的示例代碼：

#include <iostream>

struct Node {
    int data;
    Node* next;
    
    Node(int val) : data(val), next(nullptr) {}
};

Node* reverseLinkedList(Node* head) {
    Node* prev = nullptr;
    Node* current = head;
    Node* next = nullptr;
    
    while (current != nullptr) {
        next = current->next;
        current->next = prev;
        prev = current;
        current = next;
    }
    
    return prev;
}

void printLinkedList(Node* node) {
    while (node != nullptr) {
        std::cout << node->data << " ";
        node = node->next;
    }
    std::cout << std::endl;
}

int main() {
    Node* head = new Node(1);
    head->next = new Node(2);
    head->next->next = new Node(3);

    std::cout << "Original Linked List: ";
    printLinkedList(head);

    head = reverseLinkedList(head);

    std::cout << "Reversed Linked List: ";
    printLinkedList(head);

    return 0;
}

在這個示例中，我們定義了一個簡單的Node結構來表示鏈表的節點，并實現了reverseLinkedList函數來反轉鏈表。我們還實現了printLinkedList函數來打印鏈表的內容。在main函數中，我們創建了一個包含三個節點的鏈表，并打印出原始鏈表和反轉后的鏈表。