Delete a Node in BST

// code here:

TreeNode* inSuc(TreeNode* root){

    TreeNode* cur = root;

    while(cur->left) cur = cur->left;

    return cur;

}

TreeNode* deleteNode(TreeNode* root, int k){

    int cur = root->data;

    if(cur < k){

        root->right = deleteNode(root->right, k);

    }

    else if(cur > k){

        root->left = deleteNode(root->left, k);

    }

    else{

        if(root->left == NULL and root->right == NULL){

            free(root);

            return NULL;

        }

        else if(root->left == NULL){

            TreeNode* tmp = root->right;

            free(root);

            return tmp;

        }

        else if(root->right == NULL){

            TreeNode* tmp = root->left;

            free(root);

            return tmp;

        }

        

        //2 children case:

        //find in successor

        TreeNode* tmp = inSuc(root->right);

        root->data = tmp->data;

        root->right = deleteNode(root->right, tmp->data);

    }

    return root;

}