From 235c081fc40eaabc936075150a76f4197cf114e2 Mon Sep 17 00:00:00 2001
From: toeii <toeii.dyy@gmail.com>
Date: Thu, 11 Jul 2019 17:08:03 +0800
Subject: [PATCH 1/2] leetcode 0173 java code

---
 .../Solution.java                             | 29 +++++++++++++++++++
 1 file changed, 29 insertions(+)
 create mode 100644 solution/0173.Binary Search Tree Iterator/Solution.java

diff --git a/solution/0173.Binary Search Tree Iterator/Solution.java b/solution/0173.Binary Search Tree Iterator/Solution.java
new file mode 100644
index 0000000000000..f5cb244742915
--- /dev/null
+++ b/solution/0173.Binary Search Tree Iterator/Solution.java	
@@ -0,0 +1,29 @@
+public class Solution {
+    
+    private TreeNode currentNode = null;
+    private Stack<TreeNode> stack = new Stack<TreeNode>();
+
+    public binarySearchTreeIterator(TreeNode root) {
+        if (root != null) {
+            currentNode = root;
+        }
+    }
+
+    public boolean hasNext() {
+        return currentNode != null || !stack.isEmpty();
+    }
+
+    public TreeNode next() {
+        while (currentNode != null) {
+            stack.push(currentNode);
+            currentNode = currentNode.left;
+        }
+
+        currentNode = stack.pop();
+        TreeNode node = currentNode;
+        currentNode = currentNode.right;
+
+        return node;
+    }
+    
+}
\ No newline at end of file

From e1f0db465ca1e357602b680637439bb97808603d Mon Sep 17 00:00:00 2001
From: Toeii <toeii.dyy@gmail.com>
Date: Thu, 11 Jul 2019 22:11:33 +0800
Subject: [PATCH 2/2] Update Solution.java

---
 .../Solution.java                             | 65 +++++++++++++------
 1 file changed, 46 insertions(+), 19 deletions(-)

diff --git a/solution/0173.Binary Search Tree Iterator/Solution.java b/solution/0173.Binary Search Tree Iterator/Solution.java
index f5cb244742915..26a33cffe1848 100644
--- a/solution/0173.Binary Search Tree Iterator/Solution.java	
+++ b/solution/0173.Binary Search Tree Iterator/Solution.java	
@@ -1,29 +1,56 @@
 public class Solution {
-    
-    private TreeNode currentNode = null;
-    private Stack<TreeNode> stack = new Stack<TreeNode>();
 
-    public binarySearchTreeIterator(TreeNode root) {
-        if (root != null) {
-            currentNode = root;
-        }
-    }
+    /**
+     * Definition for a binary tree node.
+     * public class TreeNode {
+     *     int val;
+     *     TreeNode left;
+     *     TreeNode right;
+     *     TreeNode(int x) { val = x; }
+     * }
+     */
 
-    public boolean hasNext() {
-        return currentNode != null || !stack.isEmpty();
+    class TreeNode {
+          int val;
+          TreeNode left;
+          TreeNode right;
+          TreeNode(int x) { val = x; }
     }
 
-    public TreeNode next() {
-        while (currentNode != null) {
-            stack.push(currentNode);
-            currentNode = currentNode.left;
+    class BSTIterator {
+
+        Stack<TreeNode> stack = new Stack<>();
+
+        public BSTIterator(TreeNode root) {
+            while (root!=null){
+                stack.add(root);
+                root=root.left;
+            }
         }
 
-        currentNode = stack.pop();
-        TreeNode node = currentNode;
-        currentNode = currentNode.right;
+        /** @return whether we have a next smallest number */
+        public boolean hasNext() {
+            return !stack.isEmpty();
+        }
 
-        return node;
+        /** @return the next smallest number */
+        public int next() {
+            TreeNode current = stack.pop();
+            TreeNode res  = current;
+            current =current.right;
+            while (current!=null){
+                stack.push(current);
+                current = current.left;
+            }
+            return res.val;
+        }
     }
+
+    /**
+     * Your BSTIterator object will be instantiated and called as such:
+     * BSTIterator obj = new BSTIterator(root);
+     * int param_1 = obj.next();
+     * boolean param_2 = obj.hasNext();
+     */
     
-}
\ No newline at end of file
+}