在C中存儲任何數據類型的二叉樹

Question

我目前正在c中實現一個二叉樹。 在使代碼能夠插入整數后，我現在希望樹能夠存儲任何日期類型，例如char等。我對此感到困惑。 我聽說過/可以在節點結構中使用void *，但不確定如何在插入元素和比較void *以查看更大或更小的方面實現此目標。 任何幫助將不勝感激！ 謝謝

 #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

您應該使用void指針插入值，然后再將其轉換為它們的假定類型。

問題是，如果您知道以后要比較哪個更大或更小，您就不會“獲得任何東西”。 我想您可能希望在您的節點中有一個附加信息，該信息指定實際值的類型。

我想您想進行練習，但是實際上您是否真的想將字符數組與整數進行比較？

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;
}