Which of the following algorithmic changes correctly adapts the solution?
hard🎤 Interviewer Follow-up Q15 of Q15
Greedy Algorithms - Best Time to Buy and Sell Stock II
Suppose the problem is modified so that you can buy and sell the same stock multiple times on the same day (i.e., unlimited transactions including multiple buys and sells per day). Which of the following algorithmic changes correctly adapts the solution?
AAdd all positive differences between consecutive prices and also consider zero differences as profitable
BSum all positive differences between consecutive days as before, no change needed
CUse a dynamic programming approach to consider multiple transactions per day explicitly
DModify the code to add all positive differences between consecutive prices including zero differences
Step-by-Step Solution
Solution:
Step 1: Understand the new constraint
Allowing multiple transactions per day does not change the fact that profit comes from positive price differences.
Step 2: Check if algorithm needs change
Summing all positive consecutive differences already accounts for all profitable transactions, including multiple per day.
Final Answer:
Option B -> Option B
Quick Check:
Algorithm already sums all positive increments, no modification needed [OK]
Quick Trick:Unlimited transactions per day still sum positive differences [OK]
Common Mistakes:
MISTAKES
Adding zero or negative differences incorrectly
Overcomplicating with DP when greedy suffices
Thinking multiple transactions per day require new logic
Trap Explanation:
PITFALL
Candidates think multiple transactions per day require complex DP, but greedy sum suffices.
Interviewer Note:
CONTEXT
Tests if candidate understands problem constraints and algorithm robustness to variants.
Master "Best Time to Buy and Sell Stock II" in Greedy Algorithms
3 interactive learning modes - each teaches the same concept differently
