0101 - Symmetric Tree

0101 - Symmetric Tree

Given the root of a binary tree, check whether it is a mirror of itself (i.e., symmetric around its center).

Examples

Input: root = [1,2,2,3,4,4,3] Output: true

Input: root = [1,2,2,null,3,null,3] Output: false

Contraints

The number of nodes in the tree is in the range [1, 1000]. -100 <= Node.val <= 100

Java Solution

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode() {}
 *     TreeNode(int val) { this.val = val; }
 *     TreeNode(int val, TreeNode left, TreeNode right) {
 *         this.val = val;
 *         this.left = left;
 *         this.right = right;
 *     }
 * }
 */
class Solution {
    public boolean isSymmetric(TreeNode root) {
        return isMirror(root.left, root.right);
    }
    
    public boolean isMirror(TreeNode root1, TreeNode root2) {
        if(root1 == null && root2 == null) return true;
        if(root1 == null || root2 == null) return false;
                
        return root1.val==root2.val && isMirror(root1.left, root2.right) && isMirror(root1.right, root2.left);
    }
}