Which modification to the inversion algorithm correctly generalizes the inversion to this n-ary tree?
hard🎤 Interviewer Follow-up Q15 of Q15
Tree: Depth-First Search - Invert Binary Tree
Suppose you want to invert a binary tree where nodes can have an arbitrary number of children (not just two). Which modification to the inversion algorithm correctly generalizes the inversion to this n-ary tree?
ASwap only the first and last child pointers recursively, leaving others unchanged.
BUse BFS to swap children pairwise at each level without recursion.
CRecursively invert each child's subtree, then reverse the list of children in-place.
DInvert only the leftmost and rightmost subtrees recursively, ignoring middle children.
Step-by-Step Solution
Step 1: Understand inversion for binary tree swaps left and right children
For n-ary trees, inversion means reversing the order of children after inverting each child's subtree.
Step 2: Generalize recursion and reversal
Recursively invert each child's subtree, then reverse the children list to mirror the tree structure.
Step 3: Evaluate other options
Swapping only first and last or partial BFS swaps do not fully invert the tree structure.
Final Answer:
Option C -> Option C
Quick Check:
Recursion plus reversing children list generalizes inversion correctly [OK]
Quick Trick:Invert subtrees recursively, then reverse children list for n-ary trees [OK]
Common Mistakes:
MISTAKES
Swapping only some children pairs
Ignoring recursion on all children
Using BFS without recursion for full inversion
Trap Explanation:
PITFALL
Partial swaps or BFS-only approaches miss full inversion of subtree structures in n-ary trees.
Interviewer Note:
CONTEXT
Tests ability to generalize binary tree inversion to n-ary trees and adapt recursion accordingly.
Master "Invert Binary Tree" in Tree: Depth-First Search
3 interactive learning modes - each teaches the same concept differently
