## 实验3 选择结构程序设计 ### 实验任务 3-1.c 运行结果截图：结果1：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1525578-20210409-1617950799408) 结果2：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1525578-20210419-1618823038906) 3-2.c 运行结果截图：结果1：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1525578-20210419-1618823369476) 结果2：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1525578-20210419-1618823389598) 3-3.c 运行结果截图：有折扣的运行结果：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1525578-20210422-1619093440849) 无折扣的运行结果：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1525578-20210419-1618823563950) 3-4.c 运行结果截图：结果1：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1525578-20210422-1619093715853) 结果2：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1525578-20210422-1619093747687) ### 上机练习 1、输入一个整数，输出它的绝对值。 - 方法1的代码 ```c #include #include { int a,b; scanf("%d",&a); b = fabs(a); printf("%d\n",b); return 0; } ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1525578-20210422-1619095168618) - - 方法2的代码 ```c #include int main() { int x; scanf("%d",&x); if(x > 0) x=-x; printf("%d",x); return 0; } ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1525578-20210422-1619095645060) 2、输入一个字符，判断该字符是否是数字，若为数字，输出1，否则输出0。 - 代码 ```c #include #include int main() { char ch; scanf("%c",&ch); if(isdigit(ch)==1) printf("1"); else printf("0"); return 0; } ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1525578-20210423-1619145891699) 3、 [课后题3]，至少用两种方法实现，对比思考哪一种方法更好一些？ - 多分支方法实现的代码 ```c #include int main() { int x,y; printf("shu ru yi ge shu zi:"); scanf("%d",&x); if (x<0) y=0; else if(x<10) y=x; else if(x<20) y=x+1; else if(x<30) y=2*x-1; else if(x>=30) y=3*x+1; printf("%d",y); return 0; } ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1525578-20210423-1619147184821) - if嵌套方法实现的代码 ```c #include int main() { int x,y; printf("qing shu ru yi ge shu zi:"); scanf("%d",&x); if(x<0) y=0; else { if(x<10) y=x; else { if(x<20) y=x+1; else { if(x<30) y=2*x-1; else y=3*x+1; } } } printf("%d",y); return 0; } ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1525578-20210423-1619147818304) - 哪一种方法更好：方法2 4、 [课后题3]，至少用两种方法实现，对比思考哪一种方法更好一些？ - 任务一：练习PPT中最后一页里的菜谱题目，利用数字1-7表示的代码 ```c #include int main() { int a; printf("input integer number:"); scanf("%d",&a); switch (a) { case 1:printf("qing cai"); break; case 2:printf("ji"); break; case 3:printf("yu"); break; case 4:printf("rou"); break; case 5:printf("ji dan"); break; case 6:printf("dou zhi pin"); break; case 7:printf("hai xian"); break; default:printf("error\n"); } return 0; } ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1525578-20210423-1619155840556) - 任务二：[课后题4]输入星期首字母，判断星期几，当遇到S或T时，需要再输入一个字母，从而判断出准确日期的代码 ```c #include int main(void) { char month; printf("shu ru zi mu："); scanf("%c", &month); switch (month) { case 'M': printf("xin qi yi\n"); break; case 'm': printf("xin qi yi\n"); break; case 'T': printf("jing zai shu ru yi ge zi mu："); getchar(); scanf("%c", &month); if (month == 'U' || month == 'u') printf("xin qi er\n"); else if (month == 'H' || month == 'h') printf("xin qi si\n"); else printf("cuo wu！\n"); break; case 't': printf("qing zai shu ru yi ge zi mu："); getchar(); scanf("%c", &month); if (month == 'U' || month == 'u') printf("xin qi er\n"); else if (month == 'H' || month == 'h') printf("xin qi si\n"); else printf("cuo wu！\n"); break; case 'W': printf("xin qi san\n"); break; case 'w': printf("xin qi san\n"); break; case 'F': printf("xin qi wu\n"); break; case 'f': printf("xin qi wu\n"); break; case 'S': printf("qing zai shu ru yi ge zi mu："); getchar(); scanf("%c", &month); if (month == 'U' || month == 'u') printf("xin qi tian\n"); else if (month == 'A' || month == 'a') printf("xin qi liu\n"); else printf("cuo wu！\n"); break; case 's': printf("qing zai shu ru yi ge zi mu："); getchar(); scanf("%c", &month); if (month == 'U' || month == 'u') printf("xin qi tian\n"); else if (month == 'A' || month == 'a') printf("xin qi liiu\n"); else printf("cuo wu！\n"); break; default: printf("cuo wu！\n"); break; } return 0; } ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1525578-20210505-1620199666722)

“程序设计基础II”实验报告