C If、elseif和else陳述句根據用戶的答案產生不正確的答案

我試圖為此代碼遵循的規則是：

計算折扣百分比、門票總折扣價和節省的金額。

告訴用戶折扣、門票的總價以及用戶節省了多少。

用戶可以輸入大寫和小寫 Y/N

例如，當用戶輸入 10 張票時，有一個學生，但沒有一個客戶。折扣是 10%，90 美元，10 美元節省。

然而

當用戶輸入 6 張票時，他們是新客戶，但不是學生。折扣應該是 15%、51 美元和 9 美元的節省，但程式不會計算這個并說折扣是 0%、60 美元和 0 美元的節省......

我試圖將最后一個條件從else ifto更改else，唯一的區別是另一個計算是錯誤的。這使我相信，從根本上說，我沒有正確地做某事。

請記住，我對 C 比較陌生。這是代碼：

#include <iostream>

using namespace std;

float numberTickets;
char customer;
char student;
float totalPrice;

int main()
{
   
    float discountCustomer;
    float discountStudent;
    float discountBoth;
    float savings;
    float savingsCustomer;
    float savingsStudent;

    cout<<"How many tickets are you purchasing? ";
    cin>>numberTickets;
    cout<<"Are you a new customer (Y/N): ";
    cin>>customer;
    cout<<"Are you a student (Y/N): ";
    cin>>student;

    if (customer=='N' || customer=='n' && student=='N' || student=='n'){
        cout<<"You will receive a discount of 0%"<<endl;
    }else if (student=='Y' || student=='y' && customer=='N' || customer=='n'){
        cout<<"You will receive a discount of 10%"<<endl;
    }else if (customer=='Y' || customer=='y' && student=='N' || student=='n'){
        cout<<"You will receive a discount of 15%"<<endl;
    }else if (customer=='Y' || customer=='y' && student=='Y' || student=='y'){
        cout<<"You will receive a discount of 25%"<<endl;
    }

    totalPrice = (numberTickets)*10;
    discountCustomer = (totalPrice)*(0.85);
    discountStudent = (totalPrice)*(0.90);
    discountBoth = (totalPrice)*(0.75);
    savings = (totalPrice)-(discountBoth);
    savingsCustomer = (totalPrice)-(discountCustomer);
    savingsStudent = (totalPrice)-(discountStudent);

    if (customer=='N' || customer=='n' && student=='N' || student=='n'){
        cout<<"Your price for "<<numberTickets<<" ticket(s) is $"<<totalPrice<<endl;
    }else if (student=='Y' || student=='y' && customer=='N' || customer=='n'){
        cout<<"Your price for "<<numberTickets<<" ticket(s) is $"<<discountStudent<<endl;
    }else if (customer=='Y' || customer=='y' && student=='N' || student=='n'){
        cout<<"Your price for "<<numberTickets<<" ticket(s) is $"<<discountCustomer<<endl;
    }else if (customer=='Y' || customer=='y' && student=='Y' || student=='y'){
        cout<<"Your price for "<<numberTickets<<" ticket(s) is $"<<discountBoth<<endl;
    }

    if (customer=='N' || customer=='n' && student=='N' || student=='n'){
        cout<<"You saved $0"<<endl;
    }else if (student=='Y' || student=='y' && customer=='N' || customer=='n'){
        cout<<"You saved $"<<savingsStudent<<endl;
    }else if (customer=='Y' || customer=='y' && student=='N' || student=='n'){
        cout<<"You saved $"<<savingsCustomer<<endl;
    }else if (customer=='Y' || customer=='y' && student=='Y' || student=='y'){
        cout<<"You saved $"<<savings<<endl;
}
    return 0;
}

uj5u.com熱心網友回復：

仔細檢查運算子優先級的規則。特別要注意 的&&優先級高于||。

因此，考慮如下一行：

if (customer=='N' || customer=='n' && student=='N' || student=='n')

添加一些額外的括號以明確編譯器如何對它們進行分組：

if ((customer=='N') || ((customer=='n') && (student=='N')) || (student=='n'))

當你真正的意思是：

if ((customer=='N' || customer=='n') && (student=='N' || student=='n'))

uj5u.com熱心網友回復：

對我來說，似乎最好避免使用if非常復雜的陳述句。您基本上有四種選擇：不打折、學生打折、新客戶打折和兩者都打折。

我首先設定一個變數來指示他們是否是新客戶和/或學生：

unsigned char student;
unsigned char customer;

int is_student = std::tolower(student) == 'y';
int is_customer = std::tolower(customer) == 'y';

由于我們使用的是tolower，我們需要確保這些值不是負數，所以我已經使用unsigned char了它們。

然后我會將這兩個事實組合成一個數字，這樣我就可以將它們用作索引來在表格中查找正確的折扣：

double discount_table[] = { 100.0, 0.85, 0.90, 0.75 };

std::size_t discount_index = is_customer   2 * is_student;

double discounted_price = raw_price * discount_table[discount_index];

uj5u.com熱心網友回復：

我讀了你的代碼，你知道它很簡單，但是寫得又長又復雜，我不確定我能告訴你最簡單的代碼，但是比現在的代碼更好，而不是使用這么多 if/else 你可以選擇開關，我用開關解決了你的問題，所以看看，所有變數都是一樣的，我只是在代碼中定義了一個新的額外變數'num'。我正在共享影像，請查看代碼的代碼行號以按順序理解它。 在此處輸入影像描述

在此處輸入影像描述

在此處輸入影像描述

在此處輸入影像描述

標籤：C if 语句

上一篇：如何使用其他屬性的條件設定布爾屬性？

下一篇：在輸入中獲取字串并將其列印在C中折疊