## 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/uid1525573-20210409-1617947075830) 结果2：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1525573-20210409-1617947135295) 3-2.c 运行结果截图：结果1：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1525573-20210409-1617947513388) 结果2：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1525573-20210409-1617947595587) 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/uid1525573-20210409-1617947967231) 无折扣的运行结果：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1525573-20210409-1617948009587) 3-4.c 运行结果截图：结果1：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1525573-20210409-1617948602555) 结果2：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1525573-20210409-1617948691443) ### 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,h; printf("enter an integer a: "); scanf("%d",&a); h=fabs(a); printf("the absolute value of a is %d",h); return 0; } ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1525573-20210409-1617948988345) - - 方法2的代码 ```c #include #include int main() { int a,h; printf("please enter a : "); scanf("%d",&a); if(a>=0) { printf("the absolute value of a is%d",a); } else { h=0-a; printf("the absolute value of a is%d ",h); } return 0; } ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1525573-20210409-1617949336283) 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() { int a,h; printf("please enter a : "); scanf("%d",&a); if(a>=0) { printf("the absolute value of a is%d",a); } else { h=0-a; printf("the absolute value of a is%d ",h); } return 0; } ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1525573-20210409-1617950158901) 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() { double x,y; if(x<0) { y=0; printf("x=%lf,y=%lf",x,y); } else if(x>=0&&x<10) { y=x; printf("x=%lf,y=%lf",x,y); } else if(x>=10&&x<20) { y=x+1; printf("x=%lf,y=%lf",x,y); } else if(x>=20&&x<30) { y=2*x-1; printf("x=%lf,y=%lf",x,y); } else if(x>=30) { y=3*x+1; printf("x=%lf,y=%lf",x,y); } return 0; } ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1525573-20210409-1617951023518) - if嵌套方法实现的代码 ```c #include int main() { double x,y; if(x<0) { y=0; printf("x=%lf,y=%lf",x,y); } if(x>=0&&x<10) { y=x; printf("x=%lf,y=%lf",x,y); } if(x>=10&&x<20) { y=x+1; printf("x=%lf,y=%lf",x,y); } if(x>=20&&x<30) { y=2*x-1; printf("x=%lf,y=%lf",x,y); } if(x>=30) { y=3*x+1; printf("x=%lf,y=%lf",x,y); } return 0; } ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1525573-20210409-1617952061758) - 哪一种方法更好： 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 d; printf("please enter the number that repressents a specific day in a week: "); scanf("%d",&d); switch(d) { case(1):printf("cubbage");break; case(2):printf("chicken");break; case(3):printf("fish");break; case(4):printf("meat");break; case(5):printf("eggs");break; case(6):printf("bean products");break; case(7):printf("marine dish");break; default:printf("the number you have just input is beyond the range");break; } return 0; } ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1525573-20210409-1617952926573) - 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 f,k,l; printf("please enter a character: "); scanf("%c",&f); if(f=='M') { printf("the day is Monday"); } else if(f=='W') { printf("the day is Wednesday"); } else if(f=='F') { printf("the day is Friday"); } else if(f=='T') { printf("please input another letter to verify that day: "); scanf("%c",&k); if(k='u') { printf("the day is Tuesday"); } else if(k=='h') { printf("the day is Thursday"); } else if(f=='S') { printf("there must be another letter to identify that day: "); scanf("%c",&l); if(l=='a') { printf("the day is Saturday"); } else if(l=='u') { printf("the day is Sunday"); } } } return 0; } ``` - 运行结果截图：

“程序设计基础II”实验报告