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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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## Java
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## Java
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```Java
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//使用統一迭代法
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class Solution {
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public boolean isValidBST(TreeNode root) {
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Stack<TreeNode> stack = new Stack<>();
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TreeNode pre = null;
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if(root != null)
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stack.add(root);
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while(!stack.isEmpty()){
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TreeNode curr = stack.peek();
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if(curr != null){
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stack.pop();
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if(curr.right != null)
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stack.add(curr.right);
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stack.add(curr);
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stack.add(null);
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if(curr.left != null)
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stack.add(curr.left);
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}else{
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stack.pop();
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TreeNode temp = stack.pop();
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if(pre != null && pre.val >= temp.val)
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return false;
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pre = temp;
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}
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}
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return true;
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}
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}
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```
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```Java
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```Java
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class Solution {
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class Solution {
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// 递归
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// 递归
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