C++ 我不明白为什么我的循环在执行时不能正常工作，它还打印了不正确的选项cout #包括 #包括 #包括 使用名称空间std； int main（） { int a，b，c，z，a1，b1，a2，b2；//变量的偏差 浮子l； 字符选择； 对于（；；） { cout

您的代码结构错误，您正在使用for循环来实现它们不是为之设计的

在do…while循环中使用switch语句，并使用一个布尔变量来告诉您何时退出

#include <iostream>
#include <conio.h>
#include <math.h>

using namespace std;

int main()
{

    int a,b,c,z,a1,b1,a2,b2; //decleration of variables
    float l;
    char opt;
    for(;;)
    {
    cout << "-----Calculator----- " <<endl <<endl;
    cout << "Press (a) to add two vectors \n";
    cout << "Press (s) to subtract two vectors \n";
    cout << "Press (m) to multiply two vectors \n";
    cout << "Press (l) to calculate the length of two vectors \n";
    cout << "Press (q) to quit \n"<<endl;
    cout << "Enter your choice: \t";
    cin>>opt;


//INPUT FOR ADDITION
        for(;opt == 'a';)
        {

        cout<<"Enter first number of vactor"<<endl;
        cin>>a1;
        cout<<"Enter second number of vactor"<<endl;
        cin>>a2;
        cout<< "The vactor is"<<" :"<<"["<<a1<<","<<a2<<"]"<<endl;
        cout<<endl;
        //-------------------------------//
        cout<<"enter the first number of vactor 2"<<endl;
        cin>>b1;
        cout<<"Enter the second number of vactor 2"<<endl;
        cin>>b2;
        //-------------------------------//
        a=a1+b1;     // Adding copmonent1 of 1st vector with component1 of 2nd vector
        b=a2+b2;     // Adding copmonent2 of 1st vector with component1 of 2nd vector    
        cout<<"The sum is"<<"["<<a<<","<<b<<"]"<<endl;
        cout<<"Press any key to cont.... \n ";
        //-------------------------------//
        getch ();
        break;
        }

//INPUT FOR SUBTRACTION
        for(;opt=='s';)
        {

        cout << "Enter 1st component of vector \n";
        cin>>a1;
        cout << "Enter 2nd component of vector \n";
        cin>>a2;
        cout << "The vector is \t : \t "<<"["<<a1<<","<<a2<<"]"<<endl;
        //-------------------------------//
        cout << "Enter 1st component of vector \n";
        cin>>b1;
        cout << "Enter 2nd component of vector \n";
        cin>>b2;
        cout << "The vector is \t : \t "<<"["<<b1<<","<<b2<<"]"<<endl;
        //-------------------------------//
        a=a1-b1;  // Subtracting copmonent1 of 1st vector with component1 of 2nd vector
        b=a2-b2;  // Subtracting copmonent2 of 1st vector with component1 of 2nd vector
        cout << "The difference is \t : \t " <<"["<<a<<","<<b<<"]"<<endl;
        cout<<"Press any key to cont.... \n ";
        //-------------------------------//
        getch ();
        break;
        }

// INPUT FOR Multiply CALCULATION
        for(;opt=='m';)
        {

        cout << "Enter 1st component of vector \n";
        cin>>a1;
        cout << "Enter 2nd component of vector \n";
        cin>>a2;
        cout << "The vector is \t : \t "<<"["<<a1<<","<<a2<<"]"<<endl;
        //-------------------------------//
        cout << "Enter 1st component of vector \n";
        cin>>b1;
        cout << "Enter 2nd component of vector \n";
        cin>>b2;
        cout << "The vector is \t : \t "<<"["<<b1<<","<<b2<<"]"<<endl;
        //-------------------------------//
        a=a1*b1;  //Multiplying copmonent1 of 1st vector with component1 of 2nd vector
        b=a2*b2;  // Multiplying copmonent2 of 1st vector with component2 of 2nd vector
        c=(a1*b1)+(a2*b2); // by formula of dot product used for vectors adding adding two products
        cout<<"The multiplication is \t : \t " <<c<<endl;
        cout<<"Press any key to cont.... \n ";
        //-------------------------------//
        getch ();
        break;
        }

// INPUT FOR LENGHTH CALCULATION
        for(;opt=='l';)
        {

        cout << "Enter 1st component of vector \n";
        cin>>a1;
        cout << "Enter 2nd component of vector \n";
        cin>>a2;
        cout << "The vector is \t : \t "<<"["<<a1<<","<<a2<<"]"<<endl;
        //-------------------------------//
        // As the formula for length is sqrt(square of component 1 + square of component 2)
        a=a1*a1; // Taking square of component 1
        b=a2*a2; // Taking square of component 2
        l=sqrt(a+b);    //taking square root of (a+b) // Taking square root of result
        cout<<"The length is \t : \t " <<l<<endl;
        cout<<"Press any key to cont.... \n ";
        //-------------------------------//
        getch ();
        break;
        }
//      Quit
        for(;opt=='q';)
        {
        cout <<"Press any key to QUIT" << endl;
        getch ();
        return 0;
        //-------------------------------//
        }
        //INCORRECT OPTION
        cout<<"The option is incorrect. PLEASE enter the correct option";
        cout<<endl;
        }
        return 0;
        }

bool quit=false；
做
{
//菜单代码
cin>>opt；
开关（opt）
{
案例“a”：
//添加代码
打破
案例s：
//减法码
打破
...
案例‘q’：
退出=真；
打破
违约：
cout>opt；
如果（opt=='a'）
{
//添加代码
}
else if（opt='s'）
{
//减法码
}
...
else if（opt=='q'）
{
退出=真；
}
其他的
{
不行，我们不知道你在寻求什么帮助，当你说“这不是我想要的，请修复它”解释你的程序有什么问题。输出是怎么错误的？输出是正确的，但当任何计算结束时，它也会在末尾打印错误的按键输入选项。这并不奇怪-这个输出周围没有条件，你期望什么？实际上我必须用这两个选项来编写程序我在do while中进行了更正，但坚持使用loop@user3073283我认为您的错误是在整个程序应该使用一个for循环的情况下，对每个选项使用一个for循环。用for循环替换do while循环，它应该可以工作。
bool quit=false；for（；！quit；）{…}
bool quit = false;
do
{
    // menu code
    cin>>opt;
    switch (opt)
    {
    case 'a':
        // adding code
        break;
    case 's':
        // substracting code
        break;
    ...
    case 'q':
        quit = true;
        break;
    default:
        cout<<"The option is incorrect. PLEASE enter the correct option";
        cout<<endl;
        break;
    }
} while (!quit);
out <<"Press any key to QUIT" << endl;
getch ();
return 0;

bool quit = false;
do
{
    // menu code
    cin>>opt;
    if (opt == 'a')
    {
        // adding code
    }
    else if (opt == 's')
    {
        // substracting code
    }
    ...
    else if (opt == 'q')
    {
        quit = true;
    }
    else
    {
        cout<<"The option is incorrect. PLEASE enter the correct option";
        cout<<endl;
    }
} while (!quit);
out <<"Press any key to QUIT" << endl;
getch ();
return 0;