Symmetric Tree

最新推荐文章于 2024-01-17 14:31:46 发布

jialuyyy

最新推荐文章于 2024-01-17 14:31:46 发布

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本文介绍了一种通过递归方法来判断二叉树是否为对称树的有效算法。通过对二叉树节点进行左右子树的比较，可以高效地确定其是否关于中心对称。

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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:

But the following is not:

The binary tree problems are always solved by recursion. We can figure the regular pattern out by observing the tree above.

public class Solution {
    public boolean isSymmetric(TreeNode root) {
        if (root == null)
            return true;
        
        return symmetric(root.left, root.right);
    }
    
    private boolean symmetric(TreeNode node1, TreeNode node2) {
        if (node1 == null && node2 == null)
            return true;
        
        if (node1 == null || node2 == null)
            return false;
            
        return (node1.val == node2.val) && symmetric(node1.left, node2.right) && symmetric(node1.right, node2.left);
    }
}