(java)Symmetric Tree

Given a binary tree, check whether it is a mirror of itself (ie, symmetric around its center).

For example, this binary tree is symmetric:

    1
   / \
  2   2
 / \ / \
3  4 4  3

But the following is not:

    1
   / \
  2   2
   \   \
   3    3

Note:
Bonus points if you could solve it both recursively and iteratively.

confused what "{1,#,2,3}" means? > read more on how binary tree is serialized on OJ.

思路:本题就是判断一个二叉树是不是对称的，树的每一层都可以用水仙花数的判断方法进行判断，只要有一层不是水仙花数就不是对称的树。

代码如下(已通过leetcode)

public class Solution {
   public boolean isSymmetric(TreeNode root) {
       if(root==null) return true;
       return isequal(root.left,root.right);
   }
   //
   public boolean isequal(TreeNode p,TreeNode q) {
    if(p==null || q==null) return p==q;
    return p.val==q.val && isequal(p.left,q.right) && isequal(p.right,q.left);
   }
}