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3687. Library Late Fee Calculator πŸ”’

Description

You are given an integer array daysLate where daysLate[i] indicates how many days late the ith 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

Solutions

Solution 1: Simulation

We define a function \(\text{f}(x)\) to calculate the late fee for each book:

\[ \text{f}(x) = \begin{cases} 1 & x = 1 \\ 2x & 2 \leq x \leq 5 \\ 3x & x > 5 \end{cases} \]

Then, for each element \(x\) in the array \(\textit{daysLate}\), we compute \(\text{f}(x)\) and sum them up to get the total late fee.

The time complexity is \(O(n)\), where \(n\) is the length of the array \(\textit{daysLate}\). The space complexity is \(O(1)\).

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class Solution:
    def lateFee(self, daysLate: List[int]) -> int:
        def f(x: int) -> int:
            if x == 1:
                return 1
            if x > 5:
                return 3 * x
            return 2 * x

        return sum(f(x) for x in daysLate)

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class Solution {
    public int lateFee(int[] daysLate) {
        IntUnaryOperator f = x -> {
            if (x == 1) {
                return 1;
            } else if (x > 5) {
                return 3 * x;
            } else {
                return 2 * x;
            }
        };

        int ans = 0;
        for (int x : daysLate) {
            ans += f.applyAsInt(x);
        }
        return ans;
    }
}

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class Solution {
public:
    int lateFee(vector<int>& daysLate) {
        auto f = [](int x) {
            if (x == 1) {
                return 1;
            } else if (x > 5) {
                return 3 * x;
            } else {
                return 2 * x;
            }
        };

        int ans = 0;
        for (int x : daysLate) {
            ans += f(x);
        }
        return ans;
    }
};

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func lateFee(daysLate []int) (ans int) {
    f := func(x int) int {
        if x == 1 {
            return 1
        } else if x > 5 {
            return 3 * x
        }
        return 2 * x
    }
    for _, x := range daysLate {
        ans += f(x)
    }
    return
}

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function lateFee(daysLate: number[]): number {
    const f = (x: number): number => {
        if (x === 1) {
            return 1;
        } else if (x > 5) {
            return 3 * x;
        }
        return 2 * x;
    };
    return daysLate.reduce((acc, days) => acc + f(days), 0);
}

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