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Program.cs
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Program.cs
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using System;
namespace CountUnivalueSubtrees
{
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;
}
}
class Program
{
static void Main(string[] args)
{
Console.WriteLine("Hello World!");
}
static int CountUnivalSubtrees(TreeNode root)
{
if (root == null)
return 0;
int count = 0;
DFS(root, ref count);
return count;
}
static bool DFS(TreeNode node, ref int count)
{
if (node.left == node.right)
{
count++;
return true;
}
var isUnique = true;
if (node.left != null)
isUnique = DFS(node.left, ref count) && isUnique && node.val == node.left.val;
if (node.right != null)
isUnique = DFS(node.right, ref count) && isUnique && node.val == node.right.val;
if (!isUnique)
return false;
count++;
return true;
}
}
}