text: //cpp
  #include "decision.h"
  
  
  std::string get_letter_grade_using_if(int grade)
  {
      std::string letter_grade;
  
      if (grade < 0 || grade > 100)
      {
          letter_grade = "Invalid input. Enter grade 0-100.";
      }
      else if (grade < 60)
      {
          letter_grade = "F";
      }
      else if (grade < 70)
      {
          letter_grade = "D";
      }
      else if (grade < 80)
      {
          letter_grade = "C";
      }
      else if (grade < 90)
      {
          letter_grade = "B";
      }
      else if (grade <= 100)
      {
          letter_grade = "A";
      }
      return letter_grade;
  }
  
  std::string get_letter_grade_using_switch(int grade)
  {
      std::string letter_grade;
      switch(grade/10)
      {
          case 0:
          case 1: 
          case 2: 
          case 3: 
          case 4: 
          case 5: 
              letter_grade = "F";
              break;
          case 6:
              letter_grade = "D";
              break;
          case 7:
              letter_grade = "C";
              break;
          case 8:
              letter_grade = "B";
              break;
          case 9:
          case 10:
              letter_grade = "A";
              break;
          default: 
              letter_grade = "Invalid input. Enter grade 0-100.";
              break;
      }
      return letter_grade;
  }