Create 230-kth-smallest-element-in-a-bst.js

Author: everthis

230-kth-smallest-element-in-a-bst.js

@@ -0,0 +1,31 @@
+/**
+ * Definition for a binary tree node.
+ * function TreeNode(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}
+ */
+const kthSmallest = function (root, k) {
+  const st = []
+  while (root !== null) {
+    st.push(root)
+    root = root.left
+  }
+  while (k !== 0) {
+    const n = st.pop()
+    k--
+    if (k === 0) return n.val
+    let right = n.right
+    while (right !== null) {
+      st.push(right)
+      right = right.left
+    }
+  }
+  return -1
+}