From bb8e7312b64b13f98ca6c6ae88260a4f57375acd Mon Sep 17 00:00:00 2001
From: Lozakaka <102352821+Lozakaka@users.noreply.github.com>
Date: Tue, 25 Apr 2023 03:25:45 -0400
Subject: [PATCH] =?UTF-8?q?Update=200098.=E9=AA=8C=E8=AF=81=E4=BA=8C?=
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新增java 統一迭代法的寫法 有通過. AC
---
 problems/0098.验证二叉搜索树.md | 30 ++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/problems/0098.验证二叉搜索树.md b/problems/0098.验证二叉搜索树.md
index 95afe680..ccb63305 100644
--- a/problems/0098.验证二叉搜索树.md
+++ b/problems/0098.验证二叉搜索树.md
@@ -259,6 +259,36 @@ public:
 
 ## Java 
 
+```Java
+//使用統一迭代法
+class Solution {
+    public boolean isValidBST(TreeNode root) {
+        Stack<TreeNode> stack = new Stack<>();
+        TreeNode pre = null;
+        if(root != null)
+            stack.add(root);        
+        while(!stack.isEmpty()){
+            TreeNode curr = stack.peek();
+            if(curr != null){
+                stack.pop();
+                if(curr.right != null)
+                    stack.add(curr.right);
+                stack.add(curr);
+                stack.add(null);
+                if(curr.left != null)
+                    stack.add(curr.left);
+            }else{
+                stack.pop();
+                TreeNode temp = stack.pop();
+                if(pre != null && pre.val >= temp.val)
+                    return false;
+                pre = temp;
+            }
+        }
+        return true;
+    }
+}
+```
 ```Java
 class Solution {
     // 递归