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Program.cs
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Program.cs
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using System;
using System.Collections.Generic;
namespace SymmetricTree
{
public class TreeNode
{
public int val;
public TreeNode left;
public TreeNode right;
public TreeNode(int x) { val = x; }
}
class Program
{
static void Main(string[] args)
{
TreeNode a = new TreeNode(1);
TreeNode b = new TreeNode(2);
TreeNode c = new TreeNode(2);
TreeNode d = new TreeNode(3);
TreeNode e = new TreeNode(4);
TreeNode f = new TreeNode(4);
TreeNode g = new TreeNode(3);
a.left = b;
a.right = c;
b.left = d;
b.right = e;
c.left = f;
c.right = g;
Console.WriteLine(IsSymmetric(a));
}
static bool IsSymmetric(TreeNode root)
{
if (root == null) return true;
return CheckSymmetric(root.left, root.right);
}
static bool CheckSymmetric(TreeNode left, TreeNode right)
{
if (left != null && right != null)
return left.val == right.val && CheckSymmetric(left.left, right.right) && CheckSymmetric(left.right, right.left);
return left == null && right == null;
}
static bool IsSymmetric_Queue(TreeNode root)
{
if (root == null) return true;
var queue = new Queue<TreeNode>();
queue.Enqueue(root.left);
queue.Enqueue(root.right);
while (queue.Count != 0)
{
var left = queue.Dequeue();
var right = queue.Dequeue();
if (left == right) continue;
if (left == null || right == null || left.val != right.val) return false;
queue.Enqueue(left.left);
queue.Enqueue(right.right);
queue.Enqueue(left.right);
queue.Enqueue(right.left);
}
return true;
}
}
}