## 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/uid1527870-20210408-1617861959148) 结果2：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1527870-20210408-1617862004235) 3-2.c 运行结果截图：结果1：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1527870-20210408-1617862481686) 结果2：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1527870-20210408-1617862539107) 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/uid1527870-20210408-1617863085474) 无折扣的运行结果：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1527870-20210408-1617863112799) 3-4.c 运行结果截图：结果1：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1527870-20210408-1617863949310)![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1527870-20210408-1617863950700) 结果2：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1527870-20210408-1617863992619) ### 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 num,Num; printf("Please enter the number :\n "); scanf("%d",&num); Num=fabs(num); printf("The %d fabs is %d",num,Num); return 0; } ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1527870-20210411-1618131454748) - - 方法2的代码 ```c #include int main() { int num; printf("请输入要求值的数: "); scanf("%d",&num); if(num<0) num=-num; printf("%d ",num); return 0; } ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1527870-20210411-1618132288587) 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() { char a; printf("Please enter num:\n"); a = getchar(); if( a>='0'&&a<='9') printf("1"); else printf("0"); return 0; } ``` - 运行结果截图![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1527870-20210411-1618132813277)： 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("x="); scanf("%d",&x); if(x<0) y=0; else if(x>=0&&x<10) y=x; else if(x>=10&&x<20) y=x+1; else if(x>=20&&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/uid1527870-20210411-1618135824520) - if嵌套方法实现的代码 ```c #include int main() { float x; printf("please enter a number"); scanf("%f",&x); if (x>30) printf("y = %f",3*x+1); else if(x>=20) printf("y = %f",2*x+1); else if(x>=10) printf("y = %f",x+1); else if(x>=0) printf("y = %f",x); else if(x<0) printf("y =0"); } ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1527870-20210413-1618309881312) - 哪一种方法更好：第二种 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 date; printf("please enter a date(1-7) "); scanf("%d",&date); switch (date) { case 1:printf("Monday:qingcai");break; case 2:printf("Tuesday:ji");break; case 3:printf("Wednesday:yu");break; case 4:printf("Thursday:rou");break; case 5:printf("Friday:jidan");break; case 6:printf("Saturday:douzhipin");break; case 7:printf("Weekday:haixian");break; default:printf("error"); } } ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1527870-20210413-1618310567003) - 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 letter1,letter2,letter3; printf("please enter a letter"); scanf("%c",&letter1); switch(letter1) { case 'M':printf("Monday");break; case 'T': if(letter1 == 'T') { printf("please enter a letter"); scanf("%c",&letter2); switch(letter2) { case 'u':printf("Tuesday");break; case 'h':printf("Thursday");break; } } break; case 'W': { printf("please enter a letter"); scanf("%c",&letter3); switch(letter3); { case 'd':printf("Wendesday");break; case 'e':printf("Weekday");break; } } break; case 'F':printf("Friday");break; case 'S':printf("Saturday");break; } } ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1527870-20210413-1618311761692)

“程序设计基础II”实验报告