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Grokking the Coding Interview Patterns in C++

Invert Binary Tree

Explore how to invert a binary tree by swapping the left and right subtrees using depth-first search. This lesson helps you understand tree transformations and apply a key coding interview pattern in C++.

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Statement

Given the root node of a binary tree, transform the tree by swapping each node’s left and right subtrees, thus creating a mirror image of the original tree. Return the root of the transformed tree.

Constraints:

  • 0≤0\leq Number of nodes in the tree ≤100\leq 100
  • −1000≤-1000 \leq Node.value ≤1000\leq 1000

Examples

Understand the problem

Let’s take a moment to make sure you’ve correctly understood the problem. The quiz below helps you check if you’re solving the correct problem:

Invert Binary Tree

1.

What is the correct mirrored tree for the given tree?

  5
 / \
6   7
   / \
  8   9
A.
  5
 / \
6   7
   / \
  8   9
B.
    5
   / \
  7   6
 / \  
9   8
C.
  5
 / \
6   7
   / \
  9   8
D.
  5
 / \
7   6
   / \
  9   8
1 / 2

Figure it out!

We have a game for you to play. Rearrange the logical building blocks to develop a clearer understanding of how to solve this problem.

Sequence - Vertical
Drag and drop the cards to rearrange them in the correct sequence.
1
2
3

Try it yourself

Implement your solution in main.cpp in the following coding playground.

C++
usercode > main.cpp
// Definition for a binary tree node

// template<class T>

// class TreeNode {

// public:

//     T data;

//     TreeNode<T>* left;

//     TreeNode<T>* right;



//     TreeNode(const T data) : data(data), left(nullptr), right(nullptr) {}

// };



TreeNode<int>* MirrorBinaryTree(TreeNode<int>* root){



    // Replace this placeholder return statement with your code

    return root;

}
Invert Binary Tree