时间戳

首页 > 解决方案 > c ++：if语句无法正常运行并进入无效输出

c++ - c ++：if语句无法正常运行并进入无效输出

问题描述

刚开始学习 c++ 并尝试制作一个自动订购系统，但是在继续使用它之前尝试运行时我遇到了这个问题：

#include <iostream>
using namespace std;

char acoustic, fender, hartwood, electric, gibson, ibanez, drums, pearl, 
roland, piano, casio;
char rolandpi, equip, string, headphone, amp, mixer, micro, tuner, pick, 
music, Yes, No;

int pay1 = 0, pay2 = 0;

int main()
{
    cout << "Welcome to the Music Shop" << endl <<endl;

    cout << "a. Acoustic Guitar" << endl;
    cout << "a.1 Fender Acoustic Guitar   - P6,900.00" << endl;
    cout << "a.2 Hartwood Acoustic Guitar - P6,300.00" << endl <<endl;

    cout << "b. Electric Guitar" << endl;
    cout << "b.1 Gibson Electric Guitar   -P8,500.00" << endl;
    cout << "b.2 Ibanez Electric Guitar   -P25,000.00" << endl <<endl;

    cout << "c. Drums" << endl;
    cout << "c.1 Pearl Drum Kits          -P27,000.00" << endl;
    cout << "c.2 Roland Electronic Drums  -P24,000.00" << endl <<endl;

    cout << "d. Piano" << endl;
    cout << "d.1 Casio Digital Piano      -P19,000.00" << endl;
    cout << "d.2 Roland Piano             -P120,000.00" << endl <<endl;

    cout << "e. Music Equipments" << endl;
    cout << "e.1 Guitar String            -P113.00" << endl;
    cout << "e.2 Headphones               -P1,600.00" << endl;
    cout << "e.3 Amplifier                -P2,800.00" << endl;
    cout << "e.4 Digital Mixer            -P4,750.00" << endl;
    cout << "e.4 Vocal Microphone         -P860.00" << endl;
    cout << "e.5 Guitar Tuner             -P537.00" << endl;
    cout << "e.6 Guitar Pick              -P360.00" << endl <<endl;

    cout << "Choose the music instrument or equipment you want to buy: ";
    cin >> music;

    switch (music)
    {
        case 'a':

        cout<< "Acoustic Guitar" << endl;
        cout<< "1. Fender Acoustic Guitar   - P6,900.00" << endl;
        cout<< "2. Hartwood Acoustic Guitar - P6,300.00" << endl <<endl;
        cout<<"Choose from the available Acoustic Guitars:";
        cin>>acoustic;

        if (acoustic == 1){
            cout<<"Enter your payment:";
            cin>>pay1;
            if (pay1=6900){
                cout<<"You have succesfully purchased Fender Acoustic Guitar"<<endl;
            }
                else if (pay1>6900){
                    pay1 -= 6900;
                    cout<<"Your change is:"<<pay1<<endl;
                }
                    else (pay1<6900);
                    {
                        cout<<"You do not have enough money"<<endl;
                    }
        }
        else if (acoustic == 2){
            cout<<"Enter your payment:";
            cin>>pay1;
            if (pay1=6300){
                cout<<"You have succesfully purchased Fender Acoustic Guitar"<<endl;
            }
                else if (pay1>6300){
                    pay1 -= 6300;
                    cout<<"Your change is:"<<pay1<<endl;
                }
                    else (pay1<6300);
                    {
                        cout<<"You do not have enough money"<<endl;
                    }
        }
        else {
            cout<<"Invalid"<<endl;
        }
    }
}

我已经检查了我的if else陈述，找不到什么问题。

输入1或2从“从可用的原声吉他中选择”后，它会继续“无效”。

标签： c++if-statementcharcomparison-operators

解决方案

char你在这里读到：

cout << "Choose from the available Acoustic Guitars:";
cin >> acoustic;

但是你int稍后将它与一行进行比较：

if (acoustic == 1) {

相反，这应该是：

if (acoustic == '1') {

还有这个：

if (pay1 = 6900) {

应该：

if (pay1 == 6900) {

因为否则无论输入什么，您都会得到不正确的输出，因为pay1 = 6900设置pay1为6900并返回6900，它被隐式转换为true.

还有这一行：

else (pay1 < 6900);

需要改为

else if (pay1 < 6900)

因为否则(pay1 < 6900)不是if语句的条件，而是在这种情况下(pay1 < 6900);发生的情况（它只是计算一个布尔值并丢弃它），导致始终打印else以下消息。"You do not have enough money"

推荐阅读