/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     struct TreeNode *left;
 *     struct TreeNode *right;
 * };
 */
/**
 * Return an array of size *returnSize.
 * Note: The returned array must be malloced, assume caller calls free().
 */

int *ptr;
int cnt;
void inorder_travel(struct TreeNode *root)
{
    if(root == NULL) return;
    ptr[cnt++] = root->val;
    inorder_travel(root->left);
    inorder_travel(root->right);
}
int node_count(struct TreeNode * root)
{   
    if(root == NULL) return 0;
    return node_count(root->left) + node_count(root->right) + 1;
}
int* preorderTraversal(struct TreeNode* root, int* returnSize) {
    *returnSize = node_count(root);
    ptr = malloc(sizeof(int) * (*returnSize)  + 2);
    cnt = 0;
    inorder_travel(root);
    return ptr;
}