## 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/uid1527860-20210408-1617861885036) 结果2：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1527860-20210408-1617862110713) 3-2.c 运行结果截图：结果1：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1527860-20210408-1617863108861) 结果2：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1527860-20210408-1617863125643) 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/uid1527860-20210408-1617863908993) 无折扣的运行结果：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1527860-20210408-1617863940319) 3-4.c 运行结果截图：结果1：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1527860-20210411-1618120818418) 结果2： ![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1527860-20210411-1618120856086) ### 上机练习 1、输入一个整数，输出它的绝对值。 #include int main() { char c; float i=-1; printf("I can get the float number's absolute value: "); scanf("%f",&i); while(1) { printf("%f ",fabs(i)); scanf("%f",&i); } system("pause"); return 0; } ```c #将修改后代码填在此处，然后删除这行文字 ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1527860-20210411-1618121184247) - - 方法2的代码 ``` #include int main() { double a; scanf("%lf",&a); printf("%lf ",(a>0)?a:-a); return 0; } - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1527860-20210411-1618121491384) 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 c; printf("please enter a character "); scanf("%c",&c); if (c>='0' && c<='9') printf("1"); else printf("0"); } ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1527860-20210411-1618128219540) ![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1527860-20210411-1618128263745) 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 `` #include int main() { float x; printf("please enter a number"); scanf("%f",&x); if (x<0) printf("y = 0"); else if (x>=0 && x<10) printf("y = %f",x); else if(x>=10 && x<20) printf("y = %f",x+1); else if(x>=20 && x<30) printf("y = %f",2*x-1); else printf("y = %f",3*x+1); }77 ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1527860-20210411-1618128482284) - 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/uid1527860-20210411-1618128833971) - 哪一种方法更好：第二个if嵌套方法实现的代码 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/uid1527860-20210411-1618128925593) - 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/uid1527860-20210411-1618129274977)

“程序设计基础II”实验报告