Given the root of a binary tree, check whether it is a mirror of itself (i.e., symmetric around its center).
Example 1:
Input: root = [1,2,2,3,4,4,3]
Output: true
Example 2:
Input: root = [1,2,2,null,3,null,3]
Output: false
Constraints:
- The number of nodes in the tree is in the range [1, 1000].
- -100 <= Node.val <= 100
/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
class Solution {
public boolean isSymmetric(TreeNode root) {
if(root==null){
return true;
}
if(root.left==null&&root.right==null){
return true;
}
return isSamed(root.left, root.right);
}
public boolean isSamed(TreeNode left, TreeNode right){
if(left==null&&right==null){
return true;
}
if(left==null&&right!=null||left!=null&&right==null){
return false;
}
if(left.val!=right.val){
return false;
}
return isSamed(left.left,right.right)&&isSamed(left.right,right.left);
}
}