Day8-9

98. Validate Binary Search Tree/98. Validate Binary Search Tree.csproj

@@ -0,0 +1,11 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net6.0</TargetFramework>
+    <RootNamespace>_98._Validate_Binary_Search_Tree</RootNamespace>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+</Project>

98. Validate Binary Search Tree/Program.cs

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+namespace _98._Validate_Binary_Search_Tree;
+
+internal class Program
+{
+    static void Main(string[] args)
+    {
+        Console.WriteLine("Hello, World!");
+    }
+}

98. Validate Binary Search Tree/Solution.cs

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

98. Validate Binary Search Tree/TreeNode.cs

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+namespace _98._Validate_Binary_Search_Tree;
+
+
+//Definition for a binary tree node.
+public class TreeNode
+{
+    public int val;
+    public TreeNode? left;
+    public TreeNode? right;
+    public TreeNode(int val = 0, TreeNode? left = null, TreeNode? right = null)
+    {
+        this.val = val;
+        this.left = left;
+        this.right = right;
+    }
+}