## 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/uid1528092-20210421-1619004696477) 结果2：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1528092-20210421-1619004573069) 3-2.c 运行结果截图：结果1：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1528092-20210421-1619004837133) 结果2：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1528092-20210421-1619005379746) 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/uid1528092-20210421-1619006360057) 无折扣的运行结果：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1528092-20210421-1619006375311) 3-4.c 运行结果截图：结果1：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1528092-20210421-1619006768389) 结果2：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1528092-20210421-1619006821632) ### 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 int main() { int a,b; printf("Please enter a:"); scanf("%d",&a); b = fabs(a); printf("b = %d",b); return 0; } ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1528092-20210421-1619008099122) - - 方法2的代码 ```c #include int main() { int a; printf("Please enter a:"); scanf("%d",&a); if(a>=0) printf("%d ",a); else printf("%d ",-a); return 0; } ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1528092-20210422-1619087843099) 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 int main() { int b; scanf("%d",&b); if(b=1) { b = 1; } printf("%d ",b); return 0; } ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1528092-20210422-1619089843013) 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; printf("Please enter x: "); scanf("%d",&x); if(x<0) printf("0 "); else if(0<=x<10) printf("x "); else if(10<=x<20) printf("x+1 "); else if(20<=x<30) printf("2x-1 "); else if(x>=30) printf("3x+1 "); return 0; } ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1528092-20210422-1619092050457) - if嵌套方法实现的代码 ```c #include int main() { int x; printf("Please enter x: "); scanf("%d",&x); if(x<0) printf("0"); if(x>=0&&x<10) printf("x"); if(x>=10&&x<20) printf("x+1"); if(x>=20&&x<30) printf("2x-1"); if(x>=30) printf("3x+1"); return 0; } ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1528092-20210422-1619093155699) - 哪一种方法更好：if嵌套更合算 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("Monday:qingcai "); break; case 2:printf("Tuesday:chicken "); break; case 3:printf("Wednesday:fish "); break; case 4:printf("Thursday:meat "); break; case 5:printf("Friday:egg "); break; case 6:printf("Saturday:bean "); break; case 7:printf("Sunday:seafood "); break; } return 0; } ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1528092-20210422-1619097078611) - 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 a,b; printf("input integer number:"); scanf("%c",&a); getchar(); switch(a) { case 'M': printf("Monday ");break; case 'T': getchar(); if("b=='u'") printf("Tuesday "); else if("b=='h'") printf("Thursdays"); else printf("error"); case 'W': printf("Wednesday ");break; case 'F': printf("Friday ");break; case 'S': getchar(); if("b=='a'") printf("Saturday "); else if("b=='u'") printf("Sunday "); else printf("error");break; default:printf("error "); break; } return 0; } ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1528092-20210422-1619100432193)

“程序设计基础II”实验报告