Mirror a Binary Tree in DSA C++ - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does it mean to mirror a binary tree?

Mirroring a binary tree means swapping the left and right children of every node in the tree, creating a mirror image of the original tree.

intermediate

Which traversal method is commonly used to mirror a binary tree?

A post-order traversal is commonly used because it processes children before the parent, allowing safe swapping of left and right subtrees.

beginner

Show the base case condition in a recursive function to mirror a binary tree.

The base case is when the current node is null (empty), then return immediately because there is nothing to mirror.

beginner

What happens to the left and right children of a node during mirroring?

The left and right children are swapped. The left child becomes the right child and the right child becomes the left child.

intermediate

Why is it important to recursively mirror the subtrees before swapping the children?

Recursively mirroring subtrees first ensures that the entire subtree is mirrored before swapping, preserving the correct mirror structure.

What is the first step in mirroring a binary tree recursively?

A Check if the current node is null

B Swap the left and right children immediately

C Print the current node value

D Create a new tree

The first step is to check if the current node is null to stop recursion if there is no node.

After mirroring the left and right subtrees, what do you do next?

A Return the current node without changes

B Delete the current node

C Add a new child node

D Swap the left and right children of the current node

After mirroring the subtrees, swap the left and right children to complete the mirror at the current node.

Which traversal order is best suited for mirroring a binary tree?

A Pre-order

B In-order

C Post-order

D Level-order

Post-order traversal is best because it processes children before the parent, allowing safe swapping.

What will be the mirror of a tree with only one node?

A The same single-node tree

B A tree with two nodes

C An empty tree

D A tree with swapped children

A single-node tree mirrored is the same tree because there are no children to swap.

If a node has left child 2 and right child 3, what will be after mirroring?

A Left child 2, right child 3

B Left child 3, right child 2

C No children

D Left child null, right child null

Mirroring swaps children, so left becomes 3 and right becomes 2.

Explain step-by-step how to mirror a binary tree using recursion.

Think about what happens at each node and how recursion helps.

Describe the changes in the tree structure after mirroring a binary tree.

Imagine flipping the tree like a reflection in a mirror.