C++ switch statement beginner exercise

Question

Can anyone please explain to me where is the error? I can't really understand😂

This is the exercise:

"Write a program that allows the user to enter the grade scored in a programming class (0-100). Modify the program so that it will notify the user of their letter grade using switch statement. 0-59 F 60-69 D 70-79 C 80-89 B 90-100 A."

And this is my code:

#include <iostream>
using namespace std;
int main()

{ int grade=0;

cin>>grade;

switch (grade)
{
case 50&&59:
cout<<"You've got a F";
break;
case 60&& 69:
cout<<"You've got a D";
break;
case 70&&79:
cout<<"Yuo've got a C";
break;
case 80&&89:
cout<<"Yuo've got a B";
break;
case 90&&99:
cout<<"Yuo've got an A";
break;
} return 0;
}

Answer 1

Switch as per the standards does not work for ranges.

A&&B is of type bool, and bool variables can hold either a true or a false. These can be converted to a 1 or a 0. So your switch block translates to :

switch (grade)
{
case 1:
cout<<"You've got a F";
break;
case 1:
cout<<"You've got a D";
break;
case 1:
cout<<"Yuo've got a C";
break;
case 1:
cout<<"Yuo've got a B";
break;
case 1:
cout<<"Yuo've got an A";
break;
}

Since all the case values are the same, the compiler throws an error.

To solve this problem, use an if else-if ... else combination.

if(grade<=59&&grade>=50)
cout<<"You've got a F";
else if(grade<=69&&grade>=60)
cout<<"You've got a D";
// Other cases follow.
// Base case for the last option.
else cout<<"You've got an A";

If you have GNU GCC as your compiler, you can also use case ranges unique to GCC:

switch(grade)
{
case 50...59:
cout<<"You've got a F";
break;
// The rest of the cases follow.
}