My English is not very good, I’m sorry.I’m a beginner and want to do a problem with Ternary search tree. The problem occurs during the insertion of the node,VS throws an exception in insert_BiTreeNode: Read access violation. 0xcdcdcdcd {key=??? left=??? mid=??? …}

I don’t know how to fix it.

Below is my code

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

typedef struct {
    int key;
    struct BiTNode *left;
    struct BiTNode *mid;
    struct BiTNode *right;
}BiTNode, *BiTree;

int Max(int a, int b, int c) {
    if (a >= b && a >= c)
        return a;
    else if (c >= a && c >= b)
        return c;
    else if (b >= a && b >= c)
        return b;
}

BiTree create_BiTreeNode(int key) {
    BiTNode* node = (BiTNode*)malloc(sizeof(BiTNode));
    node->key = key;
    node->left = NULL;
    node->right = NULL;
    return node;
}

BiTree insert_BiTreeNode(BiTNode* root, int key) {
    if (root == NULL) {
        root = create_BiTreeNode(key);
        return root;
    }
    if (key < root->key - 500) {
        root->left = insert_BiTreeNode(root->left, key);
    }
    else if (key > root->key + 500) {
        root->right = insert_BiTreeNode(root->right, key);
    }
    else {
        root->mid = insert_BiTreeNode(root->mid, key);
    }
    return root;
}

int TreeHeight(BiTNode* root)
{
    if (root == NULL) {
        return 0;
    }
    if (root->left == NULL && root->right == NULL && root->mid == NULL) {
        return 1;
    }
    return Max(TreeHeight(root->left), TreeHeight(root->right), TreeHeight(root->mid)) + 1;
}

int main(){
    BiTNode* root = NULL;

    int N;
    scanf_s("%d", &N);
    int* arr = (int*)malloc(sizeof(int)* N);
    for (int i = 0; i < N; i++) {
        scanf_s("%d", &arr[i]);
        root = insert_BiTreeNode(root, arr[i]);
    }
    int res = TreeHeight(root);
    printf("%d", res);
    free(arr);
    return 0;
}