自引用 C 结构

发布于 2024-11-03 01:25:18 字数 461 浏览 4 评论 0原文

C 语言中能否有一个包含相同结构元素的结构？我在 C 中实现二叉搜索树的第一次尝试如下：

#include <stdio.h>

struct binary_tree_node {

    int value;
    struct binary_tree_node *left = null;
    struct binary_tree_node *right = null;

};

main() {

    struct binary_tree_node t;
    t.value = 12;

    struct binary_tree_node y;
    y.value = 44;
    t.left = &y;
}

我无法弄清楚这段代码有什么问题，任何帮助将不胜感激。我意识到关于 C 中的二分搜索实现还有其他问题，但我试图用我自己的代码（当然还有一些指导）从头开始解决这个问题。谢谢！

原文

Can you have a structure in C that has elements of that same structure? My first attempt at implementing a binary search tree in C is the following:

#include <stdio.h>

struct binary_tree_node {

    int value;
    struct binary_tree_node *left = null;
    struct binary_tree_node *right = null;

};

main() {

    struct binary_tree_node t;
    t.value = 12;

    struct binary_tree_node y;
    y.value = 44;
    t.left = &y;
}

I can't figure out what's wrong with this code, any help would be appreciated. I realize there are other questions on binary search implementations in C, but I'm trying to figure this out from scratch with my own code (and some guidance of course). Thanks!

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沧笙踏歌 2024-11-10 01:25:18

删除结构声明中的 = null。您可以声明自引用，但不能设置它。

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妄想挽回 2024-11-10 01:25:18

这是 gcc 4 上的错误消息：

test.c:6: error: expected ‘:’, ‘,’, ‘;’, ‘}’ or ‘__attribute__’ before ‘=’ token
test.c: In function ‘main’:
test.c:18: error: ‘struct binary_tree_node’ has no member named ‘left’

首先，您的 null 是 C 中的 NULL。
其次，您不能为结构定义内的结构中的元素设置值。

所以，它看起来像这样：

#include <stdio.h>

struct binary_tree_node {

    int value;
    struct binary_tree_node *left;
    struct binary_tree_node *right;

};

main() {

    struct binary_tree_node t;
    t.left = NULL;
    t.right = NULL;
    t.value = 12;

    struct binary_tree_node y;
    y.left = NULL;
    t.right = NULL;
    y.value = 44;
    t.left = &y;
}

或者，您可以创建一个函数来使 left 和 right 为 NULL，

#include <stdio.h>

struct binary_tree_node {

    int value;
    struct binary_tree_node *left;
    struct binary_tree_node *right;

};

void make_null(struct binary_tree_node *x) {
    x->left = NULL;
    x->right = NULL;
}

main() {

    struct binary_tree_node t;
    make_null(&t)
    t.value = 12;

    struct binary_tree_node y;
    make_null(&y);
    y.value = 44;
    t.left = &y;
}

This is the error message on gcc 4:

test.c:6: error: expected ‘:’, ‘,’, ‘;’, ‘}’ or ‘__attribute__’ before ‘=’ token
test.c: In function ‘main’:
test.c:18: error: ‘struct binary_tree_node’ has no member named ‘left’

Firstly, you null is NULL in C.
Secondly, you cannot set a value to an element in a struct inside the struct definition.

So, it would look something like this:

#include <stdio.h>

struct binary_tree_node {

    int value;
    struct binary_tree_node *left;
    struct binary_tree_node *right;

};

main() {

    struct binary_tree_node t;
    t.left = NULL;
    t.right = NULL;
    t.value = 12;

    struct binary_tree_node y;
    y.left = NULL;
    t.right = NULL;
    y.value = 44;
    t.left = &y;
}

Or, you can create a function to make left and right NULL,

#include <stdio.h>

struct binary_tree_node {

    int value;
    struct binary_tree_node *left;
    struct binary_tree_node *right;

};

void make_null(struct binary_tree_node *x) {
    x->left = NULL;
    x->right = NULL;
}

main() {

    struct binary_tree_node t;
    make_null(&t)
    t.value = 12;

    struct binary_tree_node y;
    make_null(&y);
    y.value = 44;
    t.left = &y;
}

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稚气少女 2024-11-10 01:25:18

定义结构体时不能定义结构体内部的值。此代码片段可能会使您的项目受益：

typedef struct binary_tree_node
{
    int value;
    binary_tree left;
    binary_tree right;
} binary_tree_node, *binary_tree;

#define DATA(T) ((T)->value)
#define LEFT(T) ((T)->left)
#define RIGHT(T) ((T)->right)

You cannot define the values inside the struct when defining the struct. This code snippet may benefit your project:

typedef struct binary_tree_node
{
    int value;
    binary_tree left;
    binary_tree right;
} binary_tree_node, *binary_tree;

#define DATA(T) ((T)->value)
#define LEFT(T) ((T)->left)
#define RIGHT(T) ((T)->right)

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