Program grade without using nested ifs

[Stevebass21]

Hi, I am trying to write a program that assigns a number grade (0-100) to a corresponding letter grade. The challenge is that I cannot use nested ifs , else if etc. I can use one (if/else), if it is possible.
For example: 0-59 = F
60-69 = D
70-79 = C
80-89 = B
90 100 = A
If I get a grade that is < 0 or > 100, the user gets one more chance.

I have written most of the code, and it looks something like this:

#include <iostream>
int main ( )

{
  int number_grade = 0;
  char letter_grade = ' ';

         // User Prompt

  std::cout << "Enter your numeric grade: " << "\n";
  std::cin >> number_grade;


        if (number_grade < 0 || number_grade > 100)
       {
         std::cout << "Grade is not in range. Please enter again" << std::endl;
        } //end if


      std::cin >> number_grade;

         if (number_grade >= 90 && number_grade <= 100)
         {

          letter_grade = 'A';
             std::cout << letter_grade << std::endl;
               } //end if


         if (number_grade >= 80 && number_grade <= 89)
           {
             letter_grade = 'B';
             std::cout << letter_grade << std::endl;
                } //end if


         if (number_grade >= 70 && number_grade <=79)
         {
             letter_grade = 'C';
             std::cout << letter_grade << std::endl;
                } //end if


         if (number_grade >= 60 && number_grade <=69)
         {
             letter_grade = 'D';
             std::cout << letter_grade << std::endl;
                } // end if


         if (number_grade >= 0 && number_grade <= 59)
         {
             letter_grade = 'F';
             std::cout << letter_grade << std::endl;
                 } //end if

         std::cin.get();

            return (0);
         }

The program works fine if I enter a number < 0 or > 100 first. However, if I enter a number >= 0 or <= 100 first, it makes me enter the number twice to get the desired grade.

For example:

Please enter your numeric grade:
95
95
A

Can someone point me in the right direction here? And also is there a more efficient way to do this in spite of using the restrictions I specified?

[Lynx876]

Line 20:
std::cin >> number_grade;

You ask for input again. (:

[JLBorges]

Hint: Integer division.

[AbstractionAnon]

The challenge is that I cannot use nested ifs , else if etc.

Can you use a switch statement?

switch (number_grade/10)  // integer division will give us a number from 0 - 10
{
case 9:
case 10: letter = 'A';
              break;
case 8:   letter = 'B';
              break;
case 7:  letter = 'C';
             break;
case 6: letter = 'D';
             break;
default: letter = 'F';
}

[tntxtnt]

const char* GRADES = "FFFFFFDCBAA";
letter = GRADES[ number_grade/10 ];

[AbstractionAnon]

Very nice.

[Disch]

Lookup tables ftw.

[Stevebass21]

Thanks for the replies all. Unfortunately, my professor will not allow switch or nested ifs. It would seem the program would be much easier to write if I was allowed to use them.

The reason I asked for another input in line 20 std:: >> number_grade is because I have to give the user another chance if the grade is not in range. I can take it out but if I do the user will just get a prompt to enter again but will not be able to actually do it unless they start the program over.

[Disch]

Unfortunately, my professor will not allow switch or nested ifs. It would seem the program would be much easier to write if I was allowed to use them.

Not really. It doesn't get much easier than a lookup table.

See tntxtnt's solution.