如果条件在C++中的for循环中

if condition in a for loop in C++

本文关键字：for 循环 中的 C++ 条件 如果      更新时间：2023-10-16

我目前正在进行一个for循环，该循环显示您的姓名平均得分和但我似乎无法让分数显示出来。

输出

Enter Your Name:
Quiz 1
Quiz 2
Quiz 3
Average
Grade <- this one dont appear its on the if statement in my code

代码

using namespace std;
int main(){
    int nos[5][3]; //multi-dimention
    int r, c;
    char name[20];
    int x[3];
    int av=0;
    char l;
    do{
        system("cls");
        for(r=0; r<5; r++){ //Row
            cout<<"Enter Your Name : ";
            cin>>name;
            for(c=0; c<3; c++){ //Column
                cout<<"Enter Quiz "<<"["<<r<<"]"<<"["<<c<<"] : ";
                cin>>nos[r][c];
            }
            cout<<"Average : "<<(float)(nos[r][0]+nos[r][1]+nos[r][2])/3<<endl;
            av = ((float)nos[r][0]+nos[r][1]+nos[r][2])/3;
            if(av==0 && av<=74.99){
                cout<<"grade = 5.0"<<endl; }
            if(av ==75 && av<=76.99){
                cout<<"grade = 3.0"<<endl;  }
            if(av ==77 && av<=79.99){
                cout<<"grade = 2.75"<<endl;  }
            if(av ==80 && av<=82.99){
                cout<<"grade = 2.50"<<endl; }
            if(av ==83 && av<=84.99){
                cout<<"grade = 2.25"<<endl; }
            if(av ==85 && av<=87.99){
                cout<<"grade = 2.0"<<endl; }
            if(av ==88 && av<=90.99){
                cout<<"grade = 1.75"<<endl; }
            if(av ==91 && av<=93.99){
                cout<<"grade = 1.50"<<endl;}
            if(av ==94 && av<=96.99){
                cout<<"grade = 1.25"<<endl; }
            if(av ==97 && av<=100){
                cout<<"grade = 1.0"<<endl;}
        }
        cout<<"nTry Another [Y/N] : ";
        cin>>l;
    } while(l!='N' && l!='n');
    getch();
}

您的if条件错误
使用或（||）或设置适当的下限。

例如：

if(av==0 && av<=74.99)

你要么说

if(av>=0 && av<=74.99)

或

if(av==0 || av<=74.99)

取决于你的逻辑是什么（我想是前者）。

此外，正如Bill正确指出的那样，您应该使用if else s，而不是所有这些if s。尽管它们在您的情况下有效，但if else s是首选，因为它们可以防止逻辑错误。更好的解释如下：https://stackoverflow.com/a/1796155/2302611
所以你的代码（条件部分）应该看起来像：

if(av>=0 && av<=74.99){
    cout<<"grade = 5.0"<<endl; 
}
else if(av >=75 && av<=76.99){
    cout<<"grade = 3.0"<<endl;  
}       
else if(av >=77 && av<=79.99){
    cout<<"grade = 2.75"<<endl;  
}
else if(av >=80 && av<=82.99){
    cout<<"grade = 2.50"<<endl; 
}
else if(av >=83 && av<=84.99){
    cout<<"grade = 2.25"<<endl; 
}
else if(av >=85 && av<=87.99){
    cout<<"grade = 2.0"<<endl; 
}
else if(av >=88 && av<=90.99){
    cout<<"grade = 1.75"<<endl; 
}
else if(av >=91 && av<=93.99){
    cout<<"grade = 1.50"<<endl;
}
else if(av >=94 && av<=96.99){
    cout<<"grade = 1.25"<<endl; 
}
else if(av >=97 && av<=100){
    cout<<"grade = 1.0"<<endl;
}
else cout << "Grade not in bounds";

您的if语句逻辑是错误的，并且int不能用于存储浮点数，以下是代码更改

    #include <iostream>
#include <conio.h>
using namespace std;
int main()
{
    double nos[5][3]; //multi-dimention
    int r, c;
    char name[20];
    int x[3];
    double av = 0;
    char l;
    do{
        system("cls");
        for (r = 0; r<5; r++){ //Row
            cout << "Enter Your Name : ";
            cin >> name;
            for (c = 0; c<3; c++){ //Column                              
                cout << "Enter Quiz " << "[" << r << "]" << "[" << c << "] : ";
                cin >> nos[r][c];
            }
            av = (nos[r][0] + nos[r][1] + nos[r][2]) / 3;
            cout << "Average : " << av << endl;
            if (av >= 0 && av <= 74.99){
                cout << "grade = 5.0" << endl;
            }
            if (av >= 75 && av <= 76.99){
                cout << "grade = 3.0" << endl;
            }
            if (av >= 77 && av <= 79.99){
                cout << "grade = 2.75" << endl;
            }
            if (av >= 80 && av <= 82.99){
                cout << "grade = 2.50" << endl;
            }
            if (av >= 83 && av <= 84.99){
                cout << "grade = 2.25" << endl;
            }
            if (av >= 85 && av <= 87.99){
                cout << "grade = 2.0" << endl;
            }
            if (av >= 88 && av <= 90.99){
                cout << "grade = 1.75" << endl;
            }
            if (av >= 91 && av <= 93.99){
                cout << "grade = 1.50" << endl;
            }
            if (av >= 94 && av <= 96.99){
                cout << "grade = 1.25" << endl;
            }
            if (av >= 97 && av <= 100){
                cout << "grade = 1.0" << endl;
            }
        }
        cout << "nTry Another [Y/N] : ";
        cin >> l;
    } while (l != 'N' && l != 'n');
    getch();
    return 0;
}

using namespace std;
int main(){
    int nos[5][3]; //multi-dimention
    int r, c;
    char name[20];
    int x[3];
    int av=0;
    char l;
    do{
        system("cls");
        for(r=0; r<5; r++){ //Row
            cout<<"Enter Your Name : ";
            cin>>name;
            for(c=0; c<3; c++){ //Column
                cout<<"Enter Quiz "<<"["<<r<<"]"<<"["<<c<<"] : ";
                cin>>nos[r][c];
            }
            cout<<"Average : "<<(float)(nos[r][0]+nos[r][1]+nos[r][2])/3<<endl;
            av = ((float)nos[r][0]+nos[r][1]+nos[r][2])/3;
            if(av==0 || av<=74.99){
                cout<<"grade = 5.0"<<endl; }
            else if(av ==75 || av<=76.99){
                cout<<"grade = 3.0"<<endl;  }
            else if(av ==77 || av<=79.99){
                cout<<"grade = 2.75"<<endl;  }
            else if(av ==80 || av<=82.99){
                cout<<"grade = 2.50"<<endl; }
            else if(av ==83 || av<=84.99){
                cout<<"grade = 2.25"<<endl; }
            else if(av ==85 || av<=87.99){
                cout<<"grade = 2.0"<<endl; }
            else if(av ==88 || av<=90.99){
                cout<<"grade = 1.75"<<endl; }
            else if(av ==91 || av<=93.99){
                cout<<"grade = 1.50"<<endl;}
            else if(av ==94 || av<=96.99){
                cout<<"grade = 1.25"<<endl; }
            else(av ==97 || av<=100){
                cout<<"grade = 1.0"<<endl;}
        }
        cout<<"nTry Another [Y/N] : ";
        cin>>l;
    } while(l!='N' && l!='n');
    getch();
}
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