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What is the output of the bottom-up DP function numSquares when called with n = 1?

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Dynamic Programming: Knapsack - Perfect Squares
What is the output of the bottom-up DP function numSquares when called with n = 1?
A0
Binf
C2
D1
Step-by-Step Solution
Solution:
  1. Step 1: Initialize dp array for n=1

    dp = [0, inf]
  2. Step 2: Compute dp[1]

    Check squares ≤1: only 1. dp[1] = min(inf, 1 + dp[0]) = 1.
  3. Final Answer:

    Option D -> Option D
  4. Quick Check:

    1 is a perfect square itself -> minimal count 1 [OK]
Quick Trick: dp[1] = 1 + dp[0] = 1 [OK]
Common Mistakes:
MISTAKES
  • Forgetting dp[0] = 0 base case
  • Returning inf if base case missing
  • Off-by-one errors in loop
Trap Explanation:
PITFALL
  • Without dp[0] = 0, dp[1] remains inf causing wrong output.
Interviewer Note:
CONTEXT
  • Tests handling of base cases and boundary conditions in DP
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