230. Kth Smallest Element in a BST

leetcode.com/problems/kth-smallest-element-in-a-bst/submissions/

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode() {}
 *     TreeNode(int val) { this.val = val; }
 *     TreeNode(int val, TreeNode left, TreeNode right) {
 *         this.val = val;
 *         this.left = left;
 *         this.right = right;
 *     }
 * }
 */
// inorder with counting
class Solution {
    int cnt = 0;
    int ans;
    
    public int kthSmallest(TreeNode root, int k) {
        inorder(root, k);
        return ans;
    }
    
    public void inorder(TreeNode node, int k) {
        if(node == null) return;
        if(cnt == k) return;
        inorder(node.left, k);
        cnt++;
        if(cnt == k) {
            ans = node.val;
            return;
        }
        inorder(node.right, k);
    }
}

leetcode.com/problems/kth-smallest-element-in-a-bst/discuss/63783/Two-Easiest-In-Order-Traverse-(Java)

Two Easiest In Order Traverse (Java) - LeetCode Discuss