leetCode/leetCode_101.java at master · mehtabgill/leetCode · GitHub

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/**
 * 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 {
    boolean res = true;
    public boolean isSymmetric(TreeNode root) {
        if(root == null) return true;
       dfs(root.left, root.right);
        return res;
    }

    public void dfs(TreeNode left, TreeNode right){

        if(left == null && right == null) return;
         if(left == null || right ==null){
            res = false;
            return;
        }

        dfs(left.left, right.right);

        if(left.val != right.val){
            res = false;
            return;
        }

        dfs(left.right, right.left);
    }


//     public boolean isSymmetric(TreeNode root) {
//         if(root == null ) return true;
//         Queue<TreeNode> q = new LinkedList<>();

//         q.add(root.left);
//         q.add(root.right);

//         while(!q.isEmpty()){
//             TreeNode left = q.poll();
//             TreeNode right = q.poll();

//             if(left == null && right == null){
//                 continue;
//             }
//             if(left == null || right == null) return false;
//             if(left.val != right.val) return false;

//             q.add(left.left);
//             q.add(right.right);
//             q.add(left.right);
//             q.add(right.left);
//         }


//         return true;

//       }


}