Question

在我的一个问题集中，我需要重写一个切换到if / else语句的程序。

该程序是为了记录输入的成绩，所以如果我输入“a”，它将统计出来，当我退出程序时，它将给用户一个输入的所有成绩的最终记录。

我有两个问题，第一个是它根本不工作，它不是将字符输入读作我设置的合法字符。第二个是如何防止其他if语句在执行正确的语句后执行。

我把它设置为if / else语句中的中断。我不确定他们是否正在工作，因为该程序显然甚至不接受这些角色。

我打算让他们转到，但原来的程序有休息，所以我用它们代替。

{
int grade;
int aCount=0;
int bCount=0;
int cCount=0;
int dCount=0;
int fCount=0;

puts( "Enter the letter grades" );
puts( "Enter EOF to end input" );

while( ( grade = getchar() ) != EOF )
    {

        if( grade == 'A' && grade == 'a' )
        {
            ++aCount;
            break;
        }
        else
        {
            printf( "%s\n", "That's not a valid grade, please enter again" );
            break;
        }

        if( grade == 'B' && grade == 'b' )
        {
            ++bCount;
            break;
        }
        else
        {
            printf( "%s\n", "That's not a valid grade, please enter again" );
            break;
        }

        if( grade == 'C' && grade == 'c' )
        {
            ++cCount;
            break;
        }
        else
        {
            printf( "%s\n", "That's not a valid grade, please enter again" );
            break;
        }

        if( grade == 'D' && grade == 'd' )
        {
            ++dCount;
            break;
        }
        else
        {
            printf( "%s\n", "That's not a valid grade, please enter again" );
            break;
        }

        if( grade == 'F' && grade == 'f' )
        {
            ++fCount;
            break;
        }
        else
        {
            printf( "%s\n", "That's not a valid grade, please enter again" );
            break;
        }
    }

puts( "\nTotals for each letter grade are:" );
printf( "A: %d\n", aCount );
printf( "B: %d\n", bCount );
printf( "C: %d\n", cCount );
printf( "D: %d\n", dCount );
printf( "F: %d\n", fCount );

return 0;

}

Answer 1

虽然在if语句中使用break在语法上是正确的，但它很混乱，因为它真的打破了封闭的while语句。像这样的东西更接近你正在寻找的东西：

puts( "Enter EOF to end input" );

while( ( grade = getchar() ) != EOF ) {
    if( grade == 'A' || grade == 'a' )
        ++aCount;
    else if( grade == 'B' || grade == 'b' )
        ++bCount;
    else if( grade == 'C' || grade == 'c' )
        ++cCount;
    else if( grade == 'D' || grade == 'd' )
        ++dCount;
    else if( grade == 'F' || grade == 'f' )
        ++fCount;
    else
        printf( "That's not a valid grade, please enter again\n" );
}

puts( "\nTotals for each letter grade are:" );
printf( "A: %d\n", aCount );
printf( "B: %d\n", bCount );
printf( "C: %d\n", cCount );
printf( "D: %d\n", dCount );
printf( "F: %d\n", fCount );

return 0;
}

Answer 2

您应该将AND（＆amp;＆amp;）条件更改为OR（||）条件，以便“A”或“a”增加aCount变量。使用较大的if - else if - else链来防止重复的错误检查。只使用字符串文字可以简化错误打印语句。

if (grade == 'A' || grade == 'a') {
    ++aCount;
} else if (grade == 'B' || grade == 'b') {
    ++bCount;
} else if (grade == 'C' || grade == 'c') {
    ++cCount;
} else if (grade == 'D' || grade == 'd') {
    ++dCount;
} else if (grade == 'F' || grade == 'f') {
    ++fCount;
} else {
    printf("That's not a valid grade, please enter again");
}

Answer 3

你的条件不能同时成立。将它们更改为OR（||）

if( grade == 'D' && grade == 'd' )

等级不能同时为D和d

Answer 4

为什么不将成绩存储在数组中？

即

int grades[] = { 0, 0, 0, 0, 0 };
while( ( grade = getchar() ) != EOF )
    grade = toupper(grade);
    if (grade >= 'A' && grade <= 'E') {
        ++grades[grade - 'A']; 
    } else {
        printf("That's not a valid grade, please enter again\n");
    }
 }

将开关程序重写为if else

4 个答案: