四则运算的小程序

用C语言编写，代码如下

#include <stdio.h>
 2 #include <stdlib.h>
 3 #include <time.h>
 4 #include <math.h>
 5 
 6 int main()
 7 {
 8     int i=0;
 9     int n=0;
10     int x=0;
11     int type;
12     char flag;
13     int left, right;
14     float result;
15     printf("请输入要出的题目数量\n");
16     scanf("%d",&n);
17     srand(unsigned(time(NULL)));
18     while(x<n)
19     {
20         type = rand() % 4;
21         left = rand() % 100;
22         right = rand() % 100;
23         switch(type)
24         {
25         case 0:
26             printf("%d + %d = ?\n", left, right);
27             break;
28         case 1:
29             printf("%d - %d = ?\n", left, right);
30             break;
31         case 2:
32             printf("%d * %d = ?\n", left, right);
33             break;
34         case 3:
35             printf("%d / %d = ?\n", left, right);
36             break;
37         }
38 
39         i++;
40         while(i>=n)
41         {
42             printf("一共 %d 题\n",i); 
43             printf("继续?[Y/N]\n");
44             fflush(stdin);
45             scanf("%c",&flag);
46             if(flag=='Y'||flag=='y')
47             {
48                 printf("请输入要出的题目数量\n");
49                 scanf("%d",&n);
50                 i=0;
51                 break;
52              }
53             printf("谢谢使用！\n");
54             fflush(stdin);
55             getchar();
56             return 0;
57         }
58     }
59 }