【leetcode】修剪二叉搜索树

struct TreeNode* trimBST(struct TreeNode* root, int L, int R){
    if (NULL == root)
    {
        return NULL;
    }

    if (root->val < L)
    {
        return trimBST(root->right, L, R);
    }

    if (R < root->val)
    {
        return trimBST(root->left, L, R);
    }
    root->left = trimBST(root->left, L, R);
    root->right = trimBST(root->right, L, R);
    return root;
}