我应该如何在 C++ 中初始化链表？

Question

我有一个数组，我必须将其初始化为一个列表我尝试做什么

#include <stdio.h>
#include <string.h>

struct data_t 
{
    unsigned int id_;
    char name_ [50];
};

struct node_t
{
    node_t * next_;
    data_t data_;
};

void initialize(node_t **, const char **, const unsigned int);

int main()
{
    node_t * first = NULL;
    const char * data [3] = {"Alpha", "Bravo", "Charlie"};

    initialize(&first, data, 3);

    return 0;
}

void initialize(node_t ** head, const char ** data, const unsigned int n) {
    node_t * current = NULL;
    node_t * previous = NULL;
    for (size_t i = 0; i < n; i++)
    {
        current = new node_t;
        current->next_ = previous;
        current->data_.id_ = i+1;
        strcpy(current->data_.name_, data[i]);

        if (i == 1)
        {
            *head = previous;
            previous->next_ = current;
        } else {
            previous = current;
        }     
    }
};

next_ 只是循环并在 2 个值之间变化。我尝试了许多不同的选择，但没有任何效果。请帮忙。为什么会这样？

Answer 1

在 'first' 与 'not first' 的情况下，您需要做一些特殊的事情，您知道这一点，但错了。

在第一个 (i==0) 上，您需要设置 head 以便调用者获得指向第一个节点的指针
在后续的上，您必须将先前的下一个指针设置为指向当前。对于第一个没有先验

另外你将 current->next 设置为指向 previous，那也是错误的，这导致了你的循环

这就是您所需要的

for (size_t i = 0; i < n; i++)
{
    current = new node_t;
    current->next_ = NULL; <<<======
    current->data_.id_ = i + 1;
    strcpy(current->data_.name_, data[i]);
    if (i == 0)
        *head = current;
    else
        previous->next_ = current;
    previous = current;
   
}

Answer 2

因为你不能使用std::strings，我建议你在data_t中添加一个可以复制char数组的构造函数：

struct data_t {
    data_t(unsigned id, const char* name) :
        id_{id} // can be copied automatically
    {
        // the char array needs to be copied manually:
        std::strncpy(name_, name, sizeof name_ - 1);
        name_[sizeof name_ - 1] = '[=10=]';
    }

    unsigned int id_;
    char name_[50];
};

这样，您的 initialize 函数可以简化为

// last in `data`, first in the list:
void initialize(node_t*& head, const char** data, const unsigned int n) {
    for (unsigned int i = 0; i < n; i++) {
        // create a new `node_t` with `next_` pointing at the current `head`
        // `data_` will be initialized by calling the added constructor
        // assign the returned `node_t` to `head`
        head = new node_t{head, {i + 1, data[i]}};
    }
}

或

// first in `data`, first in the list:
void initialize(node_t*& head, const char** data, const unsigned int n) {
    for (unsigned int i = n; i > 0; --i) {
        head = new node_t{head, {i, data[i - 1]}};
    }
}

请注意，initialize 通过引用 head (&) 来简化调用：

int main() {
    node_t* first = nullptr;
    const char* data[3] = {"Alpha", "Bravo", "Charlie"};

    initialize(first, data, 3); // not &first here
}

Demo

我应该如何在 C++ 中初始化链表？

How should I initialize linked list in C++?

c++

linked-list