要求用swith实现。只要代码就行，

#include <stdio.h> 
int main()
{
    int score;
    int grade;
    scanf("%d", &score);
    grade = score / 10;
    switch (grade)
    {
    case 10:
    case 9:
        printf("优\n");
        break;
    case 8:
        printf("良");
        break;
    case 7:
        printf("中");
        break;
    case 6:
        printf("及格");
        break;
    case 5:
    case 4:
    case 3:
    case 2:
    case 1:
    case 0:
        printf("不及格");
        break;
    default:
        printf("无意义");
    }
    return 0;
}