Greedy Algorithms - Partition Labels
What is the time complexity of the optimal greedy algorithm for partitioning labels using a fixed-size array for last occurrences, given a string of length n?
What is the time complexity of the optimal greedy algorithm for partitioning labels using a fixed-size array for last occurrences, given a string of length n?
medium🪤 Complexity Trap Q13 of Q15
Step-by-Step Solution
Solution:
Step 1: Analyze last occurrence computation
We scan the string once to record last occurrence of each character in O(n).Step 2: Analyze partitioning loop
We iterate over the string once more, updating partition end in O(1) per character.Final Answer:
Option A -> Option AQuick Check:
Two linear scans over string length n -> O(n) time [OK]
Quick Trick: Two passes over string -> O(n) time [OK]
Common Mistakes:
MISTAKES- Assuming nested loops cause O(n^2)
- Confusing fixed alphabet size iteration as O(n*26)
- Thinking sorting is needed
Trap Explanation:
PITFALL- The fixed alphabet size is constant, so O(n*26) is effectively O(n), but distractors make it look larger.
Interviewer Note:
CONTEXT- Checks understanding of linear time greedy approach vs naive quadratic.
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