Traverse Binary Search Tree

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

typedef struct Node {
    int key;
    struct Node *left;
    struct Node *right;
} Node;

Node* createNode(int key) {
    Node* newNode = (Node*)malloc(sizeof(Node));
    newNode->key = key;
    newNode->left = NULL;
    newNode->right = NULL;
    return newNode;
}

Node* insert(Node* root, int key) {
    if (root == NULL) {
        return createNode(key);
    }

    if (key < root->key) {
        root->left = insert(root->left, key);
    } else if (key > root->key) {
        root->right = insert(root->right, key);
    }

    return root;
}

void preorder(Node* root) {
    if (root != NULL) {
        printf("%d,", root->key);
        preorder(root->left);
        preorder(root->right);
    }
}

int main() {
    Node* root = NULL;
    int val;
    char delimiter;

    while (scanf("%d", &val) == 1) {
        root = insert(root, val);
        
        delimiter = getchar();
        if (delimiter == '\n') {
            break;
        }
    }

    preorder(root);

    return 0;
}