101. Symmetric Tree

https://leetcode.com/problems/symmetric-tree/discuss/166375/Java-Accepted-very-simple-solution

 

class Solution {
    StringBuilder sb1 = new StringBuilder();
    StringBuilder sb2 = new StringBuilder();
    public boolean isSymmetric(TreeNode root) {
        if(root == null) return true;
        leftR(root);
        rightR(root);
        if(sb1.toString().equals(sb2.toString())) {
            return true;
        }else {
            return false;
        }
        
    }
   
    public void leftR(TreeNode root) {
        if(root != null) {
            leftR(root.left);
            sb1.append("l");
            sb1.append(root.val);
            leftR(root.right);
            sb1.append("r");
        }
            
        
 }
    
    public void rightR(TreeNode root) {
        if(root != null) {
            rightR(root.right);
            sb2.append("r");
            sb2.append(root.val);
            rightR(root.left);
            sb2.append("l");
        }
    }   
}