Greedy Algorithms - Remove K Digits (Smallest Number)
What is the space complexity of the optimal greedy algorithm using a stack to remove k digits from a number string of length n?
What is the space complexity of the optimal greedy algorithm using a stack to remove k digits from a number string of length n?
medium🪤 Complexity Trap Q6 of Q15
Step-by-Step Solution
Solution:
Step 1: Identify data structures used
The stack or builder stores up to n digits, and k removals are tracked.Step 2: Total auxiliary space includes stack and variables
Stack size can be up to n, plus counters for k, so O(n + k) space.Final Answer:
Option D -> Option DQuick Check:
Stack size dominates space, plus k counters [OK]
Quick Trick: Stack stores up to n digits, plus k counters -> O(n + k) [OK]
Common Mistakes:
MISTAKES- Forgetting stack space
- Assuming constant space
Trap Explanation:
PITFALL- Candidates often forget that the stack stores up to n digits, not just k, leading to underestimating space.
Interviewer Note:
CONTEXT- Tests understanding of auxiliary space including data structures used.
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