## 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/uid1530989-20210422-1619083979456) 结果2：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1530989-20210422-1619084333621) 3-2.c 运行结果截图：结果1：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1530989-20210422-1619085997723) 结果2：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1530989-20210422-1619086019355) 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/uid1530989-20210422-1619087113126) 无折扣的运行结果：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1530989-20210422-1619087161731) 3-4.c 运行结果截图：结果1：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1530989-20210422-1619089727010) 结果2：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1530989-20210422-1619089745992) ### 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 void main() { int a; scanf("%d",&a); printf("%d\n",abs(a)); } ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1530989-20210422-1619099800820) - - 方法2的代码 ```c #include void main() { int a; scanf("%d",&a); if(a>=0) printf("%d\n",a); else printf("%d\n",-a); } ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1530989-20210422-1619100030916) 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 using namespace std; int main() { char ch; cout << "input a num: "; cin >> ch; if (ch>='1'&&ch<='9') cout << 1 << endl; else cout << 0 << endl; system("pause"); } ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1530989-20210422-1619102295992) 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() { intх,y; printf("input x:"); scanf("%d" ,&x); if (x < 0) y=0; else if (x < 10) y=x; else if (x < 20) y-x+l ; else if (x < 30) y=2*x-1 ; else y=3*x+1; printf("y=%dn",v); return 0; } ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1530989-20210422-1619105921405) - if嵌套方法实现的代码 ```c #include int main() { int x,y ; printf("input x:"); scanf("%d" ,&x); if (x<0) y=0 ; else { if(x<10) y=x; else if (x < 20) y=x+l; else if(x < 30) y=2*x-1; else y=3*x+l; } printf("y=%d]n" ,y); return 0; } 、、|、 ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1530989-20210422-1619106102656) - 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 m; printf("input m:"); scanf#included("%d" , &m) ; switch (m) { case l:printf("green vegetables\n"); break; case 2:printf("chicken\n"); break; case 3:printf("fish\n"); break; case 4:printf("meat\n"); break; case 5:printf("eggs\n"); break; case 6:printf("beans\n"); break; case 7:printf("seafood\n"); break; default:printf("error\n"); } return 0; } ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1530989-20210422-1619106739606) - 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, ch2; printf("input ch:"); scanf("%c" ,&ch); switch(ch) { case 'M' :printf ("Monday"); break ; case 'T' : ch2=getchar(); printf("input ch2:"); scanf ("%c", &ch2); if(ch2=='u') printf("Tuesday\n"); else if(ch2=='h') printf("Thursday\n"); else printf("error\n"); break; case 'W' :printf("Wednesday\n"); break ; case 'F' :printf("Friday\n"); break; case 'S' : ch2=getchar() printf("input ch2:"); scanf("%c" ,&ch2); if (ch2=='a') printf("chicken\n"); else if(ch2=='u') printf("Thursday\n"); else printf("error\n"); break; default:printf("error\n"); } return 0; } ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1530989-20210423-1619107463523)

“程序设计基础II”实验报告