自引用C结构

Question

你能在C中有一个具有相同结构元素的结构吗？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,任何帮助都会受到赞赏.我意识到在C中有关于二进制搜索实现的其他问题,但我试图用我自己的代码从头开始解决这个问题(当然还有一些指导).谢谢!

Answer 1

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,你null是NULL在C.其次,你不能在值在结构定义内的结构设置为一个元件.

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左和右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;
}

Answer 2

删除= null结构声明中的.您可以声明自引用,但不能设置它.