Greedy Algorithms - Wiggle Subsequence
Given the following code implementing the optimal wiggle subsequence algorithm, what is the output for input nums = [1, 7, 4, 9, 2, 5]?
Given the following code implementing the optimal wiggle subsequence algorithm, what is the output for input nums = [1, 7, 4, 9, 2, 5]?
easy🧾 Code Trace Q3 of Q15
Step-by-Step Solution
Solution:
Step 1: Trace loop iterations
Differences: 7-1=6(+), 4-7=-3(-), 9-4=5(+), 2-9=-7(-), 5-2=3(+). Each alternation increments count.Step 2: Count increments
Initial count=1, increments at each alternation -> final count=6.Final Answer:
Option D -> Option DQuick Check:
All differences alternate sign, count matches input length [OK]
Quick Trick: Count increments on sign changes in differences [OK]
Common Mistakes:
MISTAKES- Off-by-one counting
- Ignoring first element in count
Trap Explanation:
PITFALL- Candidates often forget to initialize count=1 or mishandle last_diff updates.
Interviewer Note:
CONTEXT- Tests ability to mentally execute greedy code and track state variables.
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