22 lines
592 B
C#
22 lines
592 B
C#
namespace _98._Validate_Binary_Search_Tree;
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public class Solution
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{
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public bool IsValidBST(TreeNode root)
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{
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return Rec(root, null, null);
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}
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private bool Rec(TreeNode node, int? lessThan, int? moreThan)
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{
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if ((lessThan != null && node.val >= lessThan) || (moreThan != null && node.val <= moreThan))
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return false;
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bool res = true;
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if (node.left != null)
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res &= Rec(node.left, node.val, moreThan);
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if (node.right != null)
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res &= Rec(node.right, lessThan, node.val);
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return res;
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}
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}
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