Which algorithmic approach guarantees an optimal solution for this problem?
easy🔍 Pattern Recognition Q11 of Q15
Tree: Depth-First Search - Invert Binary Tree
You are given a binary tree and asked to transform it so that every left child becomes the right child and every right child becomes the left child, effectively mirroring the tree structure. Which algorithmic approach guarantees an optimal solution for this problem?
AUse a greedy traversal swapping nodes only when a certain condition is met, to minimize swaps.
BPerform a depth-first traversal recursively, swapping left and right children after visiting subtrees.
CApply dynamic programming to store and reuse subtree inversion results to avoid recomputation.
DUse breadth-first traversal with a queue, swapping children at each level iteratively.
Step-by-Step Solution
Step 1: Understand the problem requires swapping children after their subtrees are inverted
The inversion must be done bottom-up to ensure subtrees are correctly mirrored before swapping.
Step 2: Identify the approach that recursively inverts subtrees before swapping children
Depth-first postorder traversal fits this pattern, ensuring correct inversion in O(n) time.
Final Answer:
Option B -> Option B
Quick Check:
Postorder recursion swaps children after subtree inversion [OK]
Quick Trick:Invert after recursive calls ensures correct subtree inversion [OK]
Common Mistakes:
MISTAKES
Thinking greedy swaps without recursion suffice
Confusing DP with tree inversion
Assuming BFS alone guarantees correct inversion
Trap Explanation:
PITFALL
Greedy or BFS approaches may swap prematurely or miss subtree inversion order, making them incorrect despite seeming plausible.
Interviewer Note:
CONTEXT
Tests if candidate recognizes correct traversal order for tree transformation.
Master "Invert Binary Tree" in Tree: Depth-First Search
3 interactive learning modes - each teaches the same concept differently
