Practice1小学四则运算（改进）

#include<stdio.h>
#include<stdlib.h> 
#include<time.h>
void srand(unsigned);//随机生成不同的数
void main() 
{       
    int n,i,a,b,c,d,e,f,g,h,j;       
    printf("****************************欢迎使用！************************\n");    
    printf("\n");       
    printf("1.加法运算\n");      
    printf("2.减法运算\n");      
    printf("3.乘法运算\n");      
    printf("4.除法运算\n");
    printf("0.退出程序\n");
    printf("***************************************************************\n");
    printf("请选择运算类型:");
    scanf("%d", &n);
    while(n<0||n>4)     
    {            
        printf("输入错误,请重新输入:\n");           
        scanf("%d",&n);     
    }  
    switch(n)
    {
    case 1:
        {
            printf("***************************************************************\n");
            printf("5.一位数加一位数\n");           
            printf("6.一位数加两位数\n");           
            printf("7.两位数加两位数\n"); 
            printf("***************************************************************\n");
            printf("请输入题型:");           
            scanf("%d",&i);        
            while(i<5||i>7)     
            {            
                printf("输入错误,请重新输入:\n");           
                scanf("%d",&i);     
            }         
            if(i==5)
            {
                srand((unsigned)time(NULL));
                a=rand()%10+1;
                b=rand()%10+1;
                c=a+b;
                printf("%d+%d=\n",a,b);
                printf("请输入答案:\n");
                scanf("%d",&d);
                while(d!=c)
                {
                    printf("回答错误，请重做:\n");
                    printf("%d+%d=\n",a,b);
                    scanf("%d",&d);
                }
                printf("回答正确!\n");
            }
            if(i==6)
            {
                srand((unsigned)time(NULL));
                a=rand()%10+1;
                b=rand()%100+1;
                c=a+b;
                printf("%d+%d=\n",a,b);
                printf("请输入答案:\n");
                scanf("%d",&d);
                while(d!=c)
                {
                    printf("回答错误，请重做:\n");
                    printf("%d+%d=\n",a,b);
                    scanf("%d",&d);
                }
                printf("回答正确!\n");
                
            }
            if(i==7)
            {
                srand((unsigned)time(NULL));
                a=rand()%100+1;
                b=rand()%100+1;
                c=a+b;
                printf("%d+%d=\n",a,b);
                printf("请输入答案:\n");
                scanf("%d",&d);
                while(d!=c)
                {
                    printf("回答错误，请重做:\n");
                    printf("%d+%d=\n",a,b);
                    scanf("%d",&d);
                }
                printf("回答正确!\n");
            }
            
            
            break;
        }
        
    case 2:
        {
            printf("***************************************************************\n");
            printf("5.一位数减一位数\n");           
            printf("6.两位数减一位数\n");           
            printf("7.两位数减两位数\n"); 
            printf("***************************************************************\n");
            printf("请输入题型:");           
            scanf("%d",&i);        
            while(i<5||i>7)     
            {            
                printf("输入错误,请重新输入:\n");           
                scanf("%d",&i);     
            }         
            if(i==5)
            {
                srand((unsigned)time(NULL));
                c=rand()%10+1;
                d=rand()%10+1;
                e=c-d;
                printf("%d-%d=\n",c,d);
                printf("请输入答案:\n");
                scanf("%d",&g);
                while(g!=e)
                {
                    printf("回答错误，请重做:\n");
                    printf("%d-%d=\n",c,d);
                    scanf("%d",&g);
                }
                printf("回答正确!\n");
            }
            
            if(i==6)
            {
                srand((unsigned)time(NULL));
                c=rand()%100+1;
                d=rand()%10+1;
                
                e=c-d;
                printf("%d-%d=\n",c,d);
                printf("请输入答案:\n");
                scanf("%d",&g);
                while(g!=e)
                {
                    printf("回答错误，请重做:\n");
                    printf("%d-%d=\n",c,d);
                    scanf("%d",&g);
                }
                printf("回答正确!\n");
            }
            if(i==7)
            {
                srand((unsigned)time(NULL));
                c=rand()%100+1;
                d=rand()%100+1;
                e=c-d;
                printf("%d-%d=\n",c,d);
                printf("请输入答案:\n");
                scanf("%d",&g);
                while(g!=e)
                {
                    printf("回答错误，请重做:\n");
                    printf("%d-%d=\n",c,d);
                    scanf("%d",&g);
                }
                printf("回答正确!\n");
            }
            break;
        }
        
    case 3:
        {
            printf("***************************************************************\n");
            printf("5.一位数乘一位数\n");           
            printf("6.一位数乘两位数\n");           
            printf("7.两位数乘两位数\n"); 
            printf("***************************************************************\n");
            printf("请输入题型:");           
            scanf("%d",&i);        
            while(i<5||i>7)     
            {            
                printf("输入错误,请重新输入:\n");           
                scanf("%d",&i);     
            }         
            if(i==5)
            {
                srand((unsigned)time(NULL));
                e=rand()%10+1;
                f=rand()%10+1;
                g=e*f;
                printf("%d*%d=\n",e,f);
                printf("请输入答案:\n");
                scanf("%d",&h);
                while(h!=g)
                {
                    printf("回答错误，请重做:\n");
                    printf("%d*%d=\n",e,f);
                    scanf("%d",&h);
                }
                printf("回答正确!\n");
            }
            if(i==6)
            {
                srand((unsigned)time(NULL));
                e=rand()%10+1;
                f=rand()%100+1;
                
                g=e*f;
                printf("%d*%d=\n",e,f);
                printf("请输入答案:\n");
                scanf("%d",&h);
                while(h!=g)
                {
                    printf("回答错误，请重做:\n");
                    printf("%d*%d=\n",e,f);
                    scanf("%d",&h);
                }
                printf("回答正确!\n");
            }
            if(i==7)
            {
                srand((unsigned)time(NULL));
                e=rand()%100+1;
                f=rand()%100+1;
                
                g=e*f;
                printf("%d*%d=\n",e,f);
                printf("请输入答案:\n");
                scanf("%d",&h);
                while(h!=g)
                {
                    printf("回答错误，请重做:\n");
                    printf("%d*%d=\n",e,f);
                    scanf("%d",&h);
                }
                printf("回答正确!\n");
            }
            break;
        }
    case 4:
        {
            printf("***************************************************************\n");
            printf("5.一位数除于一位数\n");           
            printf("6.两位数除于一位数\n");           
            printf("7.两位数除于两位数\n"); 
            printf("***************************************************************\n");
            printf("请输入题型:");           
            scanf("%d",&i);        
            while(i<5||i>7)     
            {            
                printf("输入错误,请重新输入:\n");           
                scanf("%d",&i);     
            }         
            if(i==5)
            {
                srand((unsigned)time(NULL));
                g=rand()%10+1;
                h=rand()%10+1;
                i=g/h;
                printf("%d/%d=\n",g,h);
                
                
                printf("请输入答案:\n");
                scanf("%d",&j);
                while(j!=i)
                {
                    printf("回答错误，请重做:\n");
                    printf("%d/%d=\n",g,h);
                    scanf("%d",&j);
                }
                printf("回答正确!\n");
                
            }
            if(i==6)
            {
                srand((unsigned)time(NULL));
                g=rand()%100+1;
                h=rand()%10+1;
                
                i=g/h;
                printf("%d/%d=\n",g,h);
                
                
                printf("请输入答案:\n");
                scanf("%d",&j);
                while(j!=i)
                {
                    printf("回答错误，请重做:\n");
                    printf("%d/%d=\n",g,h);
                    scanf("%d",&j);
                }
                printf("回答正确!\n");
            }
            if(i==7)
            {
                srand((unsigned)time(NULL));
                g=rand()%100+1;
                h=rand()%100+1;
                
                i=g/h;
                printf("%d/%d=\n",g,h);
                
                
                printf("请输入答案:\n");
                scanf("%d",&j);
                while(j!=i)
                {
                    printf("回答错误，请重做:\n");
                    printf("%d/%d=\n",g,h);
                    scanf("%d",&j);
                }
                printf("回答正确!\n");
                
            }
            break;
        }
    case 0:
        {
            printf("谢谢使用！再见！\n");
            break;
        }
 }
 
 
}

这次每次生成的题目都不同，也可以进行判断正误，但感觉代码过多重复冗杂0.0，不知如何缩进又不改变原本的功能0.0。