## 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/uid1525511-20210414-1618391105589) 结果2：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1525511-20210414-1618391114125) 3-2.c 运行结果截图：结果1：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1525511-20210414-1618392143124) 结果2：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1525511-20210414-1618392153473) 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/uid1525511-20210414-1618393534480) 无折扣的运行结果：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1525511-20210414-1618393542529) 3-4.c 运行结果截图：结果1：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1525511-20210414-1618394990049) 结果2：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1525511-20210414-1618395007662) ### 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 main() { int a,b; printf("qing shu ru yi ge zheng shu:"); scanf("%d",&a); b=fabs(a); printf("zhe ge shu de jue dui zhi shi:%d",b); return 0; } ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1525511-20210422-1619061951793) - - 方法2的代码 ```c #include int main() { int a; printf("qingsuruyigeshuzi: "); scanf("%d",&a); if(a<0) printf("zhegeshudejueduizhishi%d",-a); else printf("zhegeshudejueduizhishi%d",a); return 0; } ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1525511-20210415-1618491754023) 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)==0) printf("0"); else printf("1"); return 0; } ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1525511-20210422-1619063321956) 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("qing shu ru yi ge shu zi:"); scanf("%d",&x); if(x>=30) y=3*x+1; else if(x>=20) y=2*x-1; else if(x>=10) y=x+1; else if(x>=0) y=x; else y=0; printf("y=%d",y); return 0; } ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1525511-20210420-1618927145101) - if嵌套方法实现的代码 ```c #include int main() { int x,y; printf("qing shu ru yi ge shu:"); 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("y=%d",y); return 0; } ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1525511-20210420-1618927664745) - 哪一种方法更好：多分支更好 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("jin tian xing qi:"); scanf("%d",&a); switch(a) { case 1:printf("qingcai");break; case 2:printf("ji");break; case 3:printf("yu");break; case 4:printf("rou");break; case 5:printf("jidan");break; case 6:printf("douzhiping");break; case 7:printf("haixian");break; } return 0; } ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1525511-20210422-1619064200893) - 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() { char ch,ai,cx; printf("shuruxingqishouzimu:"); scanf("%c",&ch); switch(ch) { case 'M':printf("xingqiyi"); break; case 'T':printf("shurudiergezimu:"); scanf("%c",&ai); getchar(); switch(ai) { case 'u':printf("xingqier");break; case 'h':printf("xingqisi");break; } case 'W':printf("xingqisan"); break; case 'F':printf("xingqiwu"); break; case 'S':printf("shurudiergezimu:"); scanf("%c",&cx); getchar(); switch(cx) { case 'a':printf("xingqiliu");break; case 'u':printf("xingqitian");break; } default:printf("Unknown operator"); break; } return 0; } ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1525511-20210422-1619100839029)

“程序设计基础II”实验报告