Question

目前，我正在当地大学学习C ++课程，并获得调试任务。在这个赋值的说明中，我被告知这个代码唯一真正错误的是，第82-89行的嵌套if-else-if语句的条件是多余的，但是，我看不到另一种获取方法没有这些条件保持不变的相同结果...任何提示或类似的将不胜感激！

MemoryMappedViewStream

Answer 1

这部分else if(numOfChecks >= MID_LIMIT && numOfChecks < HIGH_LIMIT)看起来多余。如果保持范围检查的顺序，它可以简化为else if (numOfChecks < HIGH_LIMIT)，与后面的那个相同（只是不需要），这样整个部分看起来像：

//the following line runs only if the program did not terminate, so start over if-else
if (numOfChecks < LOW_LIMIT)
    multiplierValue = LOW_CHECKS;
else if (numOfChecks < MID_LIMIT)
    multiplierValue = MIDLOW_CHECKS;
else if (numOfChecks < HIGH_LIMIT)
    multiplierValue = MIDHIGH_CHECKS;
else
    multiplierValue = HIGH_CHECKS;

Answer 2

确实，所有条件都是多余的：使用算法：）

<强> Live On Coliru

#include <iomanip>
#include <map>
#include <iostream>

namespace {
    using Threshold = unsigned;
    using Rate      = double;

    static Rate constexpr BASE_COST = 10.0;

    std::map<Threshold, Rate, std::greater<> > const tariffs {
        { 0, .10},
        {20, .08},
        {40, .06},
        {60, .04},
    };

    double fee(unsigned numOfChecks) {
        auto rate = tariffs.lower_bound(numOfChecks);
        return BASE_COST + rate->second * numOfChecks;
    }
}

int main() {
    unsigned numOfChecks;
    std::cout << "Please enter the number of checks you used this month: ";

    if (std::cin >> numOfChecks) {
        std::cout 
            << "\nYour total for this month is $"
            << std::fixed << std::showpoint << std::setprecision(2) << fee(numOfChecks)
            << std::endl;
    } else {
        std::cout << "Invalid input\n";
        return 1;
    }
}

打印例如。

Please enter the number of checks you used this month: 10
Your total for this month is $11.00

Please enter the number of checks you used this month: 20
Your total for this month is $11.60

Please enter the number of checks you used this month: 30
Your total for this month is $12.40

Please enter the number of checks you used this month: 40
Your total for this month is $12.40

Please enter the number of checks you used this month: 50
Your total for this month is $13.00

Please enter the number of checks you used this month: 60
Your total for this month is $12.40

Please enter the number of checks you used this month: 70
Your total for this month is $12.80

Please enter the number of checks you used this month: 80
Your total for this month is $13.20

Please enter the number of checks you used this month: 90
Your total for this month is $13.60

Please enter the number of checks you used this month: 100
Your total for this month is $14.00

If-Else嵌套多余？

2 个答案: