kth-smallest-element-in-a-bst solution

Author: Jeongwon Na

kth-smallest-element-in-a-bst/njngwn.java

@@ -0,0 +1,37 @@
+/**
+ * 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;
+ *     }
+ * }
+ */
+class Solution {
+    int cnt = 0;
+    int result = 0;
+
+    public int kthSmallest(TreeNode root, int k) {
+        cnt = k;
+        traverseInOrder(root);
+        return result;
+    }
+
+    public void traverseInOrder (TreeNode node) {
+        if (node == null) return;
+
+        if (node.left != null) traverseInOrder(node.left);
+        cnt--;
+        if (cnt == 0) {
+            result = node.val;
+            return;
+        }
+        if (node.right != null) traverseInOrder(node.right);
+    }
+}