[leetcode] problem 230 – kth smallest element in a bst

public class  {
    int val;
    TreeNode left;
    TreeNode right;
    TreeNode(int x) { val = x; }
}

private int count = 0;
private int num = 0;

public int kthSmallest(TreeNode root, int k) {
    inorder(root, k);
    return num;
}

private void inorder(TreeNode root, int k) {
    if (root.left != null)
        inorder(root.left, k);

    if (++count == k) {
        num = root.val;
        return;
    }

    if (root.right != null)
        inorder(root.right, k);
}