Update 173-binary-search-tree-iterator.js

Author: everthis

173-binary-search-tree-iterator.js

@@ -43,3 +43,64 @@ BSTIterator.prototype.hasNext = function() {
  * var param_2 = obj.hasNext()
  */
 
+// another
+
+/**
+ * Definition for a binary tree node.
+ * function TreeNode(val) {
+ *     this.val = val;
+ *     this.left = this.right = null;
+ * }
+ */
+/**
+ * @param {TreeNode} root
+ */
+const BSTIterator = function(root) {
+  this.generator = dfsGenerator(root)
+  this.root = root
+  this.nextSmall = this.generator.next().value
+}
+function* dfsGenerator(root) {
+  if (root === null) return
+  const stack = []
+  let current = root
+  while (true) {
+    if (current) {
+      stack.push(current)
+      current = current.left
+    } else if (stack.length) {
+      const top = stack.pop()
+      yield top.val
+      current = top.right
+    } else {
+      break
+    }
+  }
+}
+
+/**
+ * @return the next smallest number
+ * @return {number}
+ */
+BSTIterator.prototype.next = function() {
+  const smallReturn = this.nextSmall
+  this.nextSmall = this.generator.next().value
+  return smallReturn
+}
+
+/**
+ * @return whether we have a next smallest number
+ * @return {boolean}
+ */
+BSTIterator.prototype.hasNext = function() {
+  return this.nextSmall !== undefined ? true : false
+}
+
+/**
+ * Your BSTIterator object will be instantiated and called as such:
+ * var obj = new BSTIterator(root)
+ * var param_1 = obj.next()
+ * var param_2 = obj.hasNext()
+ */
+
+