Symmetric-Tree

101. Symmetric Tree
Easy

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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
 

Follow up: Could you solve it both recursively and iteratively?
  /**
 * 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;
 *     }
 * }
 */
Solution:

class Solution {
    public boolean isSymmetric(TreeNode root) {
       Queue<TreeNode> que=new LinkedList<>();
        que.offer(root.left);
que.offer(root.right);
       
while(que.size()>0){
    TreeNode curr=que.poll();
    TreeNode cur=que.poll();
    
   
    if(curr==null &&cur==null){
        continue;
    }
     if(curr==null || cur==null){
        return false;
    }
    if(curr.val!=cur.val){
        return false;
    }
    que.offer(curr.left);
    que.offer(cur.right);
    que.offer(curr.right);
    que.offer(cur.left);
   
}   
   return true;         
    }
}