Given an integer array, which approach efficiently computes the length of the longest subsequence where the differences between consecutive elements alternate strictly between positive and negative values?

easy💻 Programming Q1 of Q15

Greedy Algorithms - Wiggle Subsequence

ASort the array and count alternating differences

BApply a brute-force search checking all subsequences

CUse a greedy algorithm tracking up and down trends in a single pass

DUse dynamic programming with O(n^3) complexity

Step-by-Step Solution

Solution:

Step 1: Understand the problem
The goal is to find the longest subsequence with alternating positive and negative differences.
Step 2: Choose an efficient approach
A greedy algorithm can track the last difference sign and count valid wiggles in one pass.
Final Answer:
Option C -> Option C
Quick Check:
Greedy approach is O(n) and optimal [OK]

Quick Trick: Greedy single pass tracks alternating differences [OK]

Common Mistakes:

MISTAKES

Assuming sorting helps solve the problem
Using brute force leading to exponential time
Confusing subsequence with substring

Trap Explanation:

PITFALL

Sorting the array does not preserve original order needed for subsequence

Interviewer Note:

CONTEXT

Tests understanding of the optimal approach for wiggle subsequence

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More Greedy Algorithms Quizzes

Given an integer array, which approach efficiently computes the length of the longest subsequence where the differences between consecutive elements alternate strictly between positive and negative values?

Step 1: Understand the problem

Step 2: Choose an efficient approach

Final Answer:

Quick Check:

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