Merge pull request neetcode-gh#1757 from ChrisKheng/scala

Create 0230-kth-smallest-element-in-a-bst.scala

scala/0230-kth-smallest-element-in-a-bst.scala

@@ -0,0 +1,36 @@
+/**
+ * Definition for a binary tree node.
+ * class TreeNode(_value: Int = 0, _left: TreeNode = null, _right: TreeNode = null) {
+ * var value: Int = _value
+ * var left: TreeNode = _left
+ * var right: TreeNode = _right
+ * }
+ */
+object Solution {
+ def kthSmallest(root: TreeNode, k: Int): Int = {
+ helper(root, k)._2
+ }
+
+ // Recursive in-order traversal.
+ def helper(root: TreeNode, k: Int): (Boolean, Int, Int) = {
+ if (root == null) {
+ return (false, 0, 0)
+ }
+
+ val (isInLeft, lVal, lSize) = helper(root.left, k)
+ if (isInLeft) {
+ return (true, lVal, 0)
+ } else {
+ if (k - lSize == 1) {
+ return (true, root.value, 0)
+ } else {
+ val (isInRight, rVal, rSize) = helper(root.right, k - (lSize + 1))
+ if (isInRight) {
+ return (true, rVal, 0)
+ } else {
+ return (false, 0, lSize + rSize + 1)
+ }
+ }
+ }
+ }
+}