how to enter in binary search tree by using command line - c

Question

I am student and I am beginner at C.
I want to make binary search tree by using command line.
I want to enter the number composing BTS by using command line.
I have to make it by using pointer and print it by using preorder.
I delete some code because it's too much code in this question.(delete part)
how to make it?
I can't know how to make main part.
Here is my code:
#include <stdio.h>
#include <stdlib.h>
struct node
{
int data; //정수를 보관할 노드
struct node *left_child; // 왼쪽 자식
struct node *right_child; // 오른쪽 자식
};
struct node* search(struct node *root, int x)
{
if (root=NULL || root->data==x) // root가 없거나 data가 root와 같다면 root를 리턴
return root;
else if (x > root->data)
return search(root->right_child, x);
else
return search(root->left_child, x);
}
struct node* find_minimum(struct node *root)
{
if(root==NULL)
return NULL;
else if(root->left_child != NULL)
return find_minimum(root->left_child);
return root;
}
struct node* new_node(int x)
{
struct node *p;
p = malloc(sizeof(struct node));
p->data = x;
p->left_child = NULL;
p->right_child = NULL;
return p;
}
struct node* insert(struct node *root, int x)
{
if(root==NULL)
return new_node(x);
else if(x<root->data)
root->left_child = insert(root->left_child,x);
else
root->right_child = insert(root->right_child, x);
return root;
}
void preorder(struct node *root)
{
if(root!=NULL)
{
printf("%d", root->data);
preorder(root->left_child);
preorder(root->right_child);
}
}
int main()
{
struct node *root;
int number;
int num_count = 0;
while(1)
{
scanf("%d", &number);
printf("%d", &number);
if (num_count = 0)
{
root = new_node(number);
num_count += 1;
}
else
if(number == EOF)
{
break;
}
else
{
insert(root, number);
}
}
preorder(root);
return 0;
}

Answer 1

There are multiple problems in your code:
The test if (root=NULL || root->data==x) is incorrect: = is the assignment operator, very different from the comparison operator ==. Use if (root == NULL || root->data == x)
&number is the address of variable number. Passing the address is required for scanf() to store the converted value into the destination object, but you should just pass the value to printf, without the & operator.
scanf() returns the number of successful conversions. Testing if (number == EOF) is surprising, you should test if (scanf("%d", &number) != 1) and possibly if (number < 0) if entering a negative number means end of input.
printf("%d", root->data); outputs just the digits, without any extra space or newline, causing all output to appear as a single string of digits. Add spaces and newlines to make the output more readable.
there is no need to special case the first node: initializing root as NULL and using root = insert(root, number); for each node is safer as it allows for an empty tree.
Here is a modified version:
#include <stdio.h>
#include <stdlib.h>
struct node {
int data; //정수를 보관할 노드
struct node *left_child; // 왼쪽 자식
struct node *right_child; // 오른쪽 자식
};
struct node *search(struct node *root, int x) {
if (root == NULL || root->data == x) // root가 없거나 data가 root와 같다면 root를 리턴
return root;
else
if (x > root->data)
return search(root->right_child, x);
else
return search(root->left_child, x);
}
struct node *find_minimum(struct node *root) {
if (root != NULL && root->left_child != NULL)
return find_minimum(root->left_child);
else
return root;
}
struct node *new_node(int x) {
struct node *p = malloc(sizeof(struct node));
if (p != NULL) {
p->data = x;
p->left_child = NULL;
p->right_child = NULL;
}
return p;
}
struct node *insert(struct node *root, int x) {
if (root == NULL)
return new_node(x);
else if (x < root->data)
root->left_child = insert(root->left_child, x);
else
root->right_child = insert(root->right_child, x);
return root;
}
void preorder(struct node *root) {
if (root != NULL) {
printf("%d ", root->data);
preorder(root->left_child);
preorder(root->right_child);
}
}
void free_tree(struct node *root) {
if (root != NULL) {
free_tree(root->left_child);
free_tree(root->right_child);
free(root);
}
}
int main() {
struct node *root = NULL;
int number;
while (scanf("%d", &number) == 1 && number >= 0) {
printf("%d\n", number);
root = insert(root, number);
}
preorder(root);
printf("\n");
free_tree(root);
return 0;
}