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What is the space complexity of the optimal DFS with two-value return solution for House Robber III on a tree with n nodes?

medium🪤 Complexity Trap Q6 of Q15
Tree: Depth-First Search - House Robber III (On Tree)
What is the space complexity of the optimal DFS with two-value return solution for House Robber III on a tree with n nodes?
AO(1) constant space excluding input
BO(n) due to recursion stack in worst case (skewed tree)
CO(log n) due to recursion stack in balanced tree
DO(n) due to memoization table storing all nodes
Step-by-Step Solution
Solution:
  1. Step 1: Consider recursion stack usage

    In worst case (skewed tree), recursion stack depth can be O(n).
  2. Step 2: Memoization auxiliary space

    Optimal solution uses constant auxiliary space per node, no extra table needed.
  3. Final Answer:

    Option B -> Option B
  4. Quick Check:

    Space dominated by recursion stack depth O(n) worst case [OK]
Quick Trick: Recursion stack dominates space in skewed trees [OK]
Common Mistakes:
MISTAKES
  • Forgetting recursion stack space, assuming O(1)
Trap Explanation:
PITFALL
  • Candidates often ignore recursion stack space, underestimating total space complexity.
Interviewer Note:
CONTEXT
  • Tests understanding of recursion stack space in DFS
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