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Symmetric Tree Check

Certification: Basic Level Accuracy: 100% Submissions: 1 Points: 8

Write a Java program to check if a binary tree is symmetric around its center (i.e., mirror of itself). A binary tree is symmetric if the left subtree is a mirror reflection of the right subtree.

Example 1
    

  • Input: root = [1,2,2,3,4,4,3]
    • 

  • Output: true
    • 

  • Explanation:

    Symmetric Tree Check With The Center Symmetric

      

    • The tree is symmetric around its center.
      • 

    •
Example 2
    

  • Input: root = [1,2,2,null,3,null,3]
    • 

  • Output: false
    • 

  • Explanation:

    Symmetric Tree Check With Not Symmetricity

      

    • The tree is not symmetric.
      • 

    •
Constraints
    

  • The number of nodes in the tree is in the range [1, 1000].
    • 

  • -100 ≤ Node.val ≤ 100
    • 

  • Time Complexity: O(n), where n is the number of nodes in the tree.
    • 

  • Space Complexity: O(h), where h is the height of the tree.
    •
RecursionTreeEYPhillips
Editorial

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Hint
Solution

Solution Hints

    
  
  • Use a recursive approach to check if two subtrees are mirrors of each other.
    • 
  
  • Two trees are a mirror reflection if:
   - Their root values are the same.
   - The left subtree of one tree is a mirror of the right subtree of the other.
    • 
  
  • Check if the root's left and right subtrees are mirrors of each other.
    • 
  
  • Handle base cases like empty trees or single-node trees.
    •

Steps to solve by this approach:

 Step 1: Check if the root is null. If so, return true (an empty tree is symmetric).
 Step 2: Create a helper function isMirror() to check if two subtrees are mirrors of each other.
 Step 3: In isMirror(), if both nodes are null, return true.
 Step 4: If one node is null and the other is not, return false.
 Step 5: Check if the current nodes have the same value.
 Step 6: Recursively check if left.left is a mirror of right.right and left.right is a mirror of right.left.
 Step 7: Return the result of the mirror check for the root's left and right subtrees.

Submitted Code :