Which of the following problems CANNOT be solved efficiently using the wiggle subsequence greedy pattern?

easy🔍 Pattern Recognition Q2 of Q15

Greedy Algorithms - Wiggle Subsequence

AFind the maximum length subsequence where differences alternate in sign

BFind the longest subsequence with strictly alternating positive and negative differences

CFind the length of the longest wiggle subsequence in an integer array

DFind the longest contiguous subarray with alternating signs in differences

Step-by-Step Solution

Solution:

Step 1: Analyze each problem
Options A, C, and D describe wiggle subsequence problems solvable by greedy. Finding the longest contiguous subarray with alternating signs in differences asks for contiguous subarray, which is different.
Step 2: Identify anti-pattern
Longest contiguous alternating subarray requires sliding window or DP, not wiggle subsequence greedy pattern.
Final Answer:
Option D -> Option D
Quick Check:
Only contiguous alternating subarray is not solved by wiggle subsequence pattern [OK]

Quick Trick: Contiguous alternating sequences ≠ wiggle subsequence [OK]

Common Mistakes:

MISTAKES

Trap Explanation:

PITFALL

Candidates often think wiggle subsequence pattern applies to contiguous subarrays, which it does not.

Interviewer Note:

CONTEXT

Tests candidate's ability to distinguish wiggle subsequence from similar but different problems.

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