Проверка существования структуры - C++ - Ответ 2297749

#include <stdlib.h>
#include <stdio.h>
 
typedef struct tree {
    int data;
    struct tree* left;
    struct tree* right;
} tree_t;
 
tree_t* create(int data) {
  tree_t* result = (tree_t*)malloc(sizeof(tree_t));
 
  result->data = data;
  result->left = NULL;
  result->right = NULL;
 
  return result;
}
 
void destroy(tree_t* tree) {
  if (tree == NULL)
    return;
 
  destroy(tree->left);
  destroy(tree->right);
  free(tree);
}
 
tree_t* insert(tree_t* tree, int data) {
  if (tree == NULL)
    return create(data);
 
  if (tree->data < data)
    tree->left = insert(tree->left, data);
  else if (tree->data > data)
    tree->right = insert(tree->right, data);
  
  return tree;
}
 
void traverse(tree_t* tree, void (*function)(int)) {
  if (tree == NULL)
    return;
 
  traverse(tree->left, function);
  function(tree->data);
  traverse(tree->right, function);
}
 
void print(int number) {
  printf("%d\n", number);
}
 
int main() {
  tree_t* tree = create(5);
 
  insert(tree, 4);
  insert(tree, 6);
  insert(tree, 3);
  insert(tree, 7);
  insert(tree, 2);
  insert(tree, 8);
  insert(tree, 1);
  insert(tree, 9);
  insert(tree, 0);
  insert(tree, 10);
 
  traverse(tree, print);
 
  destroy(tree);
 
  return 0;
}