Is Library Late Fee Calculator easy or hard?

Library Late Fee Calculator is an Easy difficulty problem. The main challenge is correctly implementing the fee rules and handling edge cases such as books returned on time or exactly on the due date.

Library Late Fee Calculator Python/Java solution

The implementation in Python or Java follows the same structure: loop through the records, compute overdue days, apply the fee rule, and accumulate the total. Since only basic arithmetic and conditional checks are used, the logic is short and runs in O(n) time.

How to solve Library Late Fee Calculator in O(n)?

Process the records in a single pass. For each entry, compute the number of overdue days, check whether the book was returned late, and add the corresponding penalty to a running total. Because each record requires constant work, the full algorithm runs in O(n) time.

What is the best approach for Library Late Fee Calculator?

The best approach is direct simulation. Iterate through the array of borrowing or return records, calculate how many days each item is overdue, and apply the fee rule. This processes each record once, giving O(n) time complexity and O(1) space complexity.

Is Library Late Fee Calculator asked at Google/Amazon/Meta?

Problems like Library Late Fee Calculator appear in coding screens at many companies as easy rule‑implementation tasks. They are common in early interview rounds where candidates must demonstrate correct handling of conditions, loops, and array traversal.

What data structure is used in Library Late Fee Calculator?

The primary data structure is an array containing borrowing or return records. The algorithm simply iterates through the array and applies simulation logic to compute overdue durations and fees.

What is the time complexity of Library Late Fee Calculator?

The optimal solution runs in O(n) time where n is the number of borrowing records. Each entry is processed exactly once to determine the overdue duration and compute the corresponding fee. Space complexity is O(1) because only a running total is stored.

3687. Library Late Fee Calculator - Practice Online

You are given an integer array daysLate where daysLate[i] indicates how many days late the i^th book was returned.

The penalty is calculated as follows:

If daysLate[i] == 1, penalty is 1.
If 2 <= daysLate[i] <= 5, penalty is 2 * daysLate[i].
If daysLate[i] > 5, penalty is 3 * daysLate[i].

Return the total penalty for all books.

Example 1:

Input: daysLate = [5,1,7]

Output: 32

Explanation:

daysLate[0] = 5: Penalty is 2 * daysLate[0] = 2 * 5 = 10.
daysLate[1] = 1: Penalty is 1.
daysLate[2] = 7: Penalty is 3 * daysLate[2] = 3 * 7 = 21.
Thus, the total penalty is 10 + 1 + 21 = 32.

Example 2:

Input: daysLate = [1,1]

Output: 2

Explanation:

daysLate[0] = 1: Penalty is 1.
daysLate[1] = 1: Penalty is 1.
Thus, the total penalty is 1 + 1 = 2.

Constraints:

1 <= daysLate.length <= 100
1 <= daysLate[i] <= 100