kth samllest element in a bst

Author: eunhwa99

kth-smallest-element-in-a-bst/eunhwa99.kt

@@ -0,0 +1,18 @@
+class Solution {
+    // TC : O(H+K)
+    // SC: O(H)
+    private var K: Int = 0
+    fun kthSmallest(root: TreeNode?, k: Int): Int {
+        K = k
+        return traverse(root)!!.`val`
+    }
+
+    fun traverse(cur: TreeNode?): TreeNode?{
+        if(cur == null) return cur
+
+        val result = traverse(cur.left)
+        K--
+        if(K == 0) return cur
+        return result ?: traverse(cur.right)
+    }
+}