C++：用switch语句怎么编这个程序，最好把这个程序写出来吧

#include
int main()
{
int score; char grade;
printf("请输入学生成绩：");
scanf("%d", &score);

if (score > 100 || score < 0)
printf("\n输入成绩有误！\n");
else
{
switch (score - score % 10)
{
case 100:
case 90:
grade = 'A';
break;

case 80:
grade = 'B';
break;

case 70:
grade = 'C';
break;

case 60:
grade = 'D';
break;

default:
grade = 'E';
break;
}
}
printf("\n成绩等级是：%c\n", grade);
}

switch(score)
{case ....}

//80-89，90-100类似60-69
switch(score)
{
case 60:
case 61:
case 62:
case 63:
case 64:
case 65:
case 66:
case 67:
case 68:
case 69:
grade='D';

break;

case 70:
case 71:
case 72:
case 73:
case 74:
case 75:
case 76:
case 77:
case 78:
case 79:
grade='C';

break;
default：
grade='E';

break;
}

写了半天，也测试了，希望采纳
#include
#include
#include

int main( )
{
int score;
char grade;
printf("请输入成绩: ");
scanf("%d",&score);
if(score>100||score<0)printf("\n输入成绩有误\n");
switch (score/10){
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';break;
}
printf("%c",grade);
return 0;
}