在c中存储任何数据类型的二叉树

Question

我目前正在 c 中实现二叉树。在让代码工作以插入整数之后，我现在希望树能够存储任何日期类型，即 char 等。我对如何去做这件事有点难过。我听说/看到我可以在我的节点结构中使用 void*，但不确定如何在插入元素和比较 void* 以查看哪个更大或更小方面实现这一点。任何帮助将不胜感激！谢谢

 #include <stdio.h>
 #include <stdlib.h>

//struct for node of the binary tree
struct node
{
    void *value;
    struct node *p_left;
    struct node *p_right;
};

//recursive function to allow users to input into the tree
void insert(void* key, struct node** leaf )
{

if( *leaf == NULL )
{
    *leaf = (struct node*) malloc( sizeof( struct node ) );
    (*leaf)->value = key;
    (*leaf)->p_left = NULL;
    (*leaf)->p_right = NULL;
    printf(  "\nnew node " );
}
else if( key < (*leaf)->value )
   {
    printf(  "\ngoing left " );
    insert( key, &(*leaf)->p_left );

   }
else if(key > (*leaf)->value)
   {
    printf(  "\ngoing right " );
    insert( key, &(*leaf)->p_right );
   }
}

int main(void)
{
struct node *p_root = NULL;
int value ; //i want value to be of any kind

printf(  "\nPlease enter a value: " );
scanf( "%d", &value );
insert(value,  &p_root);

return 0;
   }

Answer 1

您应该使用 void 指针来插入值，然后将它们转换为它们假定的类型。

问题是，如果您知道以后要比较哪个更大或更小，您就不想得到“任何东西”。我想你可能想在你的节点中有一个额外的信息来指定实际的值是什么类型。

我想你想这样做是为了练习，但实际上你真的想将字符数组与整数进行比较吗？

Answer 2

#include <stdio.h>
#include <stdlib.h>

struct node {
    void *value;
    struct node *p_left;
    struct node *p_right;
};

typedef int (*Compare)(const void *, const void *);

void insert(void* key, struct node** leaf, Compare cmp){
    if( *leaf == NULL ){
        *leaf = (struct node*) malloc( sizeof( struct node ) );
        (*leaf)->value = key;
        (*leaf)->p_left = NULL;
        (*leaf)->p_right = NULL;
        printf(  "\nnew node " );
    } else if( cmp(key,  (*leaf)->value) < 0) {
        printf(  "\ngoing left " );
        insert( key, &(*leaf)->p_left, cmp);
    } else if( cmp(key, (*leaf)->value) > 0){
        printf(  "\ngoing right " );
        insert( key, &(*leaf)->p_right, cmp);
    } else {
        free(key);
    }
}

int CmpInt(const int *a, const int *b){
    return *a < *b ? -1 : *a > *b;
}

int *GetInteger(void){
    char line[16];
    printf("Please enter a value : ");
    if(fgets(line, sizeof line, stdin)){
        int v, *ret;
        char *p;
        v = strtol(line, &p, 10);
        if(*p == '\n' || *p == '\0'){
            int *ret = malloc(sizeof(*ret));
            *ret = v;
            return ret;
        }
    }
    return NULL;
}

void print_tree(struct node *root, void (*print_func)(const void*) ){
    if(root){
        print_tree(root->p_left, print_func);
        print_func(root->value);
        print_tree(root->p_right, print_func);
    }
}

void print_int(const void *p){
    printf("%d ", *(int*)p);
}

int main(void){
    struct node *p_root = NULL;
    void *value;//int *value;

    while(value = GetInteger()){//upto input EOF or invalid input
        insert(value,  &p_root, (Compare)CmpInt);
    }

    print_tree(p_root, print_int);
    //release tree omit 
    return 0;
}