LeetCode 101 Symmetric Tree

LeetCode Symmetric Tree

题目来源 https://leetcode.com/problems/symmetric-tree/description/

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

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

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