Java for LeetCode 101 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

解题思路：

重载一个isSymmetric判断两棵树是否对称即可，JAVA实现如下：

public boolean isSymmetric(TreeNode root) {
if(root==null)
return true;
return isSymmetric(root.left,root.right);
}
public boolean isSymmetric(TreeNode left,TreeNode right){
if(left==null||right==null)
return left==null&&right==null;
if(left.val!=right.val)
return false;
return(isSymmetric(left.left,right.right)&&isSymmetric(left.right,right.left));
}