Task20.对称二叉树

LeetCode101.对称二叉树

题目

代码

一，递归

/** 
  * Definition for a binary tree node. 
  * public class TreeNode { 
  *     public int val; 
  *     public TreeNode left; 
  *     public TreeNode right; 
  *     public TreeNode(int x) { val = x; } 
  * } 
  */
public class Solution 
{    
    public bool IsSymmetric(TreeNode root) 
    {        
        return IsMirror(root,root);    
    }    

    public bool IsMirror(TreeNode t1, TreeNode t2)    
    {        
        if (t1 == null && t2 == null)            
            return true;        
        if (t1 == null || t2 == null || t1.val != t2.val)            
            return false;        
        return IsMirror(t1.right,t2.left) && IsMirror(t1.left,t2.right);    
    }
}

二，迭代

/** 
  * Definition for a binary tree node. 
  * public class TreeNode { 
  *     public int val; 
  *     public TreeNode left; 
  *     public TreeNode right; 
  *     public TreeNode(int x) { val = x; } 
  * } 
  */ 
public class Solution 
{    
    public bool IsSymmetric(TreeNode root) 
    {        
        Queue<TreeNode> queue = new Queue<TreeNode>();        
        queue.Enqueue(root);        
        queue.Enqueue(root);        
        while (queue.Count != 0)        
        {            
            TreeNode t1 = queue.Dequeue();            
            TreeNode t2 = queue.Dequeue();            
            if (t1 == null && t2 == null)                
                continue;            
            if (t1 == null || t2 == null)                
                return false;            
            if (t1.val != t2.val)                
                return false;            
            queue.Enqueue(t1.left);            
            queue.Enqueue(t2.right);            
            queue.Enqueue(t1.right);            
            queue.Enqueue(t2.left);        
        }        
        return true;    
    }
}