//运用C语言开发一个“小学生算术四则运算测试系统”。该系统是让计算机充当一位给小学生布置作业的算术老师，为学生出题并阅卷。该系统要求实现下列功能：

//①为小学生出题（分别进行+、-、*、/等不同运算）。

//②学生做题后，进行评阅。学生每做一题后，评阅给出“答题正确，很好”或“答题错误，重做”等信息。

//③加、减、乘、除运算功能可以自由选择实现。

//④运算数值可控制在两位数的四则运算范围内。

#include <stdio.h>

#include <stdlib.h>

#include <time.h>

int c,a,b,r,ri;

void main() {

    srand( (unsigned)time( NULL ) );

    system("cls");

    printf("小学生算术四则运算测试系统\n");

    while (1) {

        printf("1加法 2减法 3乘法 4除法 0退出:");fflush(stdout);

        rewind(stdin);

        scanf("%d",&c);

        if (0==c) break;

        switch (c) {

        case 1:

            a=rand()%100;

            b=rand()%100;

            r=a+b;

            while (1) {

                printf("%d+%d=?",a,b);fflush(stdout);

                rewind(stdin);

                scanf("%d",&ri);

                if (ri==r) {

                    printf("答题正确，很好！\n");

                    break;

                } else {

                    printf("答题错误，请重做。\n");

                }

            }

        break;

        case 2:

            a=1+rand()%99;

            b=rand()%a;

            r=a-b;

            while (1) {

                printf("%d-%d=?",a,b);fflush(stdout);

                rewind(stdin);

                scanf("%d",&ri);

                if (ri==r) {

                    printf("答题正确，很好！\n");

                    break;

                } else {

                    printf("答题错误，请重做。\n");

                }

            }

        break;

        case 3:

            a=rand()%99;

            b=rand()%99;

            r=a*b;

            while (1) {

                printf("%d*%d=?",a,b);fflush(stdout);

                rewind(stdin);

                scanf("%d",&ri);

                if (ri==r) {

                    printf("答题正确，很好！\n");

                    break;

                } else {

                    printf("答题错误，请重做。\n");

                }

            }

        break;

        case 4:

            a=2+rand()%998;

            b=1+rand()%(a/2);

            while (1) {

                if (0==a%b) break;

                b--;

            }

            r=a/b;

            while (1) {

                printf("%d/%d=?",a,b);fflush(stdout);

                rewind(stdin);

                scanf("%d",&ri);

                if (ri==r) {

                    printf("答题正确，很好！\n");

                    break;

                } else {

                    printf("答题错误，请重做。\n");

                }

            }

        break;

        }

    }

}