C++和链表

#include <iostream>
#include <cstring>

using namespace std;

// 类
// 是一种高级一点的结构体
class node {
    public:
    // similar to PHP OOP Access Modifiers
        int value;
        node* next;
    
    // Why nullptr  =>  https://dzone.com/articles/what-exactly-nullptr-is-in-c
    node(int new_value, node* new_next = nullptr) {
        value = new_value;
        next = new_next;
    }
};

// 列出链表中所有node的值，用制表符隔开
int list_all(node *head) {
    cout << "All values in this linked list: ";
    while(head != nullptr) {
        cout << head->value << "\t";
        head = head->next;
    }
    cout << endl;
    return 0;
}

// 删除第n个node
int remove_element_by_id(node *head, int number) {
    // starts at 0
    node* current_ptr = head;
    for(int counter = 0; counter < number; counter++) {
        current_ptr = current_ptr->next;
        if(current_ptr->next == nullptr) {
            cout << "Out of range" << endl;
            return 1;
        }
    }
    current_ptr->value = current_ptr->next->value;
    current_ptr->next = current_ptr->next->next;
    return 0;
}

// 获取链表中最后一个node的内存地址
node* traverse_till_the_end(node* head) {
    node* current = head;
    while(current->next != nullptr) {
        current = current->next;
    }
    return current;
}

// 在链表的最后新增一个node
node* attach(int value, node* head = nullptr) {
    node* new_node = new node(value, nullptr);
    node* ptr_to_return = nullptr;
    node* last_node_in_list = nullptr;
    if(head != nullptr) {
        last_node_in_list = traverse_till_the_end(head);
        last_node_in_list->next = new_node;
        ptr_to_return = head;
    }
    else if(head == nullptr) {
        ptr_to_return = new node(value);
    }
    return ptr_to_return;
}

// 在链表的第n个node的后面插入一个node
node* insert(int value, int number, node* head) {
    node* current = head;
    for(int i = 0; i < number; i++) {
        current = current->next;
        if(current->next == nullptr) {
            cout << "Index out of range" << endl;
            return head;
        }
    }
    node* new_node = new node(value, current->next);
    current->next = new_node;
    return head;
}

int main() {

    cout << "Linked list Demo" << endl;
    
    // 手动创建一个链表
    node* node4_ptr = new node(12450);
    node* node3_ptr = new node(810   , node4_ptr);
    node* node2_ptr = new node(1919  , node3_ptr);
    node* node1_ptr = new node(114514, node2_ptr);

    // 列出链表中所有node的值
    list_all(node1_ptr);

    // 往那个链表后面新增东西
    attach(777, node1_ptr);
    // 往链表的中间插入东西
    insert(888, 1, node1_ptr);
    list_all(node1_ptr);

    // 也可以直接使用 attach() 函数创建新链表
    node* new_linkedList = attach(9527);
    list_all(new_linkedList);
    
    return 0;
}