✨ [230] my approach

Author: enkr1

230/my_solution.js

@@ -0,0 +1,74 @@
+class TreeNode {
+  constructor(val, left, right) {
+    this.val = (val === undefined ? 0 : val);
+    this.left = (left === undefined ? null : left);
+    this.right = (right === undefined ? null : right);
+  }
+}
+
+/**
+ * @param {TreeNode} root
+ * @param {number} k
+ * @return {number}
+ */
+var kthSmallest = function (root, k) {
+  let list = [], kValue = null, parents = [];
+
+  const inOrder = (node) => {
+    console.log("parents")
+    console.log(parents)
+    if (node === null || k === 0) return;
+
+    if (node.left !== null) { // going left
+      parents.push(node);
+      inOrder(node.left);
+    } else { // returning to right
+      k--;
+      kValue = node.val;
+      list.push(node.val);
+
+      if (node.right === null && parents.length > 0) {
+        console.log("r null")
+        let parent = parents.pop();
+        parent.left = null;
+        inOrder(parent);
+      } else {
+        inOrder(node.right);
+      }
+    }
+  }
+
+  inOrder(root);
+
+  return kValue;
+};
+
+
+let x =
+  // [1]
+  kthSmallest(
+    new TreeNode(1),
+    1
+  )
+// // [5,3,6,2,4,null,null,1]
+// kthSmallest(
+//   new TreeNode(
+//     5,
+//     new TreeNode(3,
+//       new TreeNode(2, new TreeNode(1)),
+//       new TreeNode(4)),
+//     new TreeNode(6)
+//   ),
+//   3
+// )
+// kthSmallest(
+//   new TreeNode(
+//     3,
+//     new TreeNode(1, null, new TreeNode(2)),
+//     new TreeNode(4)
+//   ),
+//   3
+// )
+
+console.log("x")
+console.log(x)

230/solution.js

@@ -0,0 +1,43 @@
+class TreeNode {
+  constructor(val, left, right) {
+    this.val = (val === undefined ? 0 : val);
+    this.left = (left === undefined ? null : left);
+    this.right = (right === undefined ? null : right);
+  }
+}
+
+/**
+ * @param {TreeNode} root
+ * @param {number} k
+ * @return {number}
+ */
+var kthSmallest = function (root, k) {
+  let kValue = null, parents = [];
+
+  const inOrder = (node) => {
+    console.log("parents")
+    console.log(parents)
+    if (node === null || k === 0) return;
+
+    if (node.left !== null) { // going left
+      parents.push(node);
+      inOrder(node.left);
+    } else { // returning to right
+      k--;
+      kValue = node.val;
+
+      if (node.right === null && parents.length > 0) {
+        console.log("r null")
+        let parent = parents.pop();
+        parent.left = null;
+        inOrder(parent);
+      } else {
+        inOrder(node.right);
+      }
+    }
+  }
+
+  inOrder(root);
+
+  return kValue;
+};

README.md

@@ -59,6 +59,7 @@
 - [213. House Robber II](./213/)
 - [217. Contains Duplicate](./217/)
 - [226. Invert Binary Tree](./226/)
+- [230. Kth Smallest Element in a BST](./230/)
 - [235. Lowest Common Ancestor of a Binary Search Tree](./235/)
 - [238. Product of Array Except Self](./238/)
 - [242. Valid Anagram](./242/)
@@ -145,7 +146,7 @@ Batch create:
 NOTE: JS IS HERE
 -->
 ```ssh
-chapter=235 && mkdir ./$chapter && touch ./$chapter/my_solution.js && touch ./$chapter/solution.js && alias x="node ./$chapter/my_solution.js"
+chapter=230 && mkdir ./$chapter && touch ./$chapter/my_solution.js && touch ./$chapter/solution.js && alias x="node ./$chapter/my_solution.js"
 ```
 > then you can use `x` for quick debug.