101-Symmetric Tree

Description

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

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For example, this binary tree [1,2,2,3,4,4,3] is symmetric:

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

But the following [1,2,2,null,3,null,3] is not:

    1
   / \
  2   2
   \   \
   3    3

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問題描述

給定二叉樹， 判斷該樹是否圍繞中心對稱

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問題分析

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解法

class Solution {
    public boolean isSymmetric(TreeNode root){
        return root == null ? true : isMirror(root.left, root.right);
    }

    public boolean isMirror(TreeNode node1, TreeNode node2){
        if(node1 == null && node2 == null) return true;
        if(node1 == null || node2 == null) return false;

        return node1.val == node2.val && isMirror(node1.left,node2.right) && isMirror(node1.right, node2.left);
    }
}