Dynamic Programming: Knapsack - Minimum Cost for Tickets
Given the following code snippet implementing the minimum cost tickets problem, what is the output of mincostTickets([1,4,6,7,8,20], [2,7,15])?
Given the following code snippet implementing the minimum cost tickets problem, what is the output of mincostTickets([1,4,6,7,8,20], [2,7,15])?
easy🧾 Code Trace Q3 of Q15
Step-by-Step Solution
Solution:
Step 1: Trace dp from the end for given input
Starting from day 20, dp[5] = min(2 + dp[6], 7 + dp[6], 15 + dp[6]) = 2 + 0 = 2Step 2: Calculate dp[0] by backward iteration
By iterating backward and choosing minimum costs, dp[0] sums to 11 for all days covered.Final Answer:
Option A -> Option AQuick Check:
Output matches known example result 11 [OK]
Quick Trick: Trace dp backward to find dp[0] = 11 [OK]
Common Mistakes:
MISTAKES- Misindexing dp array
- Forgetting to add dp[next_i] cost
Trap Explanation:
PITFALL- Candidates often miscalculate next_i or forget to add dp[next_i], leading to wrong totals.
Interviewer Note:
CONTEXT- Tests ability to mentally execute DP code on typical input
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