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

Author: everthis

173-binary-search-tree-iterator.js

@@ -0,0 +1,45 @@
+/**
+ * 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.root = root;
+  this.stack = [];
+};
+
+/**
+ * @return the next smallest number
+ * @return {number}
+ */
+BSTIterator.prototype.next = function() {
+  while (this.root) {
+    this.stack.push(this.root);
+    this.root = this.root.left;
+  }
+  this.root = this.stack.pop();
+  const result = this.root.val;
+  this.root = this.root.right;
+  return result;
+};
+
+/**
+ * @return whether we have a next smallest number
+ * @return {boolean}
+ */
+BSTIterator.prototype.hasNext = function() {
+  return this.root || this.stack.length;
+};
+
+/**
+ * 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()
+ */
+