分數分級

問題：

將分數依 A:100~90 B:80~89 C:70~79 D:60~69 E:0~59 分等級
做法有以下幾種：

• 用if
• 用switch+除以10
• 用除以10+陣列解(最漂亮，一行的程式就解決問題！)

1．

  //score為分數變數，浮點數，grade為等級變數，字元
  if (score <=  100 && score >= 90) grade = 'A';
  if (score <=   89 && score >= 80) grade = 'B';
  if (score <=   79 && score >= 70) grade = 'C';
  if (score <=   69 && score >= 60) grade = 'D';
  if (score <=   59) grade = 'E';

2．除以10去掉個位數，判斷上就會較簡單

    float score; char grade;
    cout << "請輸入成績："; cin >> score;

    score = (int)(score / 10); //去掉個位數

    if  (score == 10 ||
         score ==  9)  
                         grade = 'A';
    else if (score == 8) grade = 'B';  
    else if (score == 7) grade = 'C';  
    else if (score == 6) grade = 'D';  
    else                 grade = 'E';  

    cout << "你的成績等級是：" << grade << endl;

3．除以10去掉個位數，用switch

    float score; char grade;
    cout << "請輸入成績："; cin >> score;

    int s = (int)(score / 10); //去掉個位數
    switch (s) {
    case 10:
    case  9: grade = 'A'; break;
    case  8: grade = 'B'; break;
    case  7: grade = 'C'; break;
    case  6: grade = 'D'; break; 
    default: grade = 'E'; 
    }

    cout << "你的成績等級是：" << grade << endl;