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Update 0098.验证二叉搜索树.md

新增java 統一迭代法的寫法有通過. AC

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`@@ -259,6 +259,36 @@ public:`
`259`	`259`
`260`	`260`	`## Java`
`261`	`261`
	`262`	+```Java
	`263`	`+//使用統一迭代法`
	`264`	`+class Solution {`
	`265`	`+ public boolean isValidBST(TreeNode root) {`
	`266`	`+ Stack<TreeNode> stack = new Stack<>();`
	`267`	`+ TreeNode pre = null;`
	`268`	`+ if(root != null)`
	`269`	`+ stack.add(root);`
	`270`	`+ while(!stack.isEmpty()){`
	`271`	`+ TreeNode curr = stack.peek();`
	`272`	`+ if(curr != null){`
	`273`	`+ stack.pop();`
	`274`	`+ if(curr.right != null)`
	`275`	`+ stack.add(curr.right);`
	`276`	`+ stack.add(curr);`
	`277`	`+ stack.add(null);`
	`278`	`+ if(curr.left != null)`
	`279`	`+ stack.add(curr.left);`
	`280`	`+ }else{`
	`281`	`+ stack.pop();`
	`282`	`+ TreeNode temp = stack.pop();`
	`283`	`+ if(pre != null && pre.val >= temp.val)`
	`284`	`+ return false;`
	`285`	`+ pre = temp;`
	`286`	`+ }`
	`287`	`+ }`
	`288`	`+ return true;`
	`289`	`+ }`
	`290`	`+}`
	`291`	+```
`262`	`292`	```Java
`263`	`293`	`class Solution {`
`264`	`294`	`// 递归`

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