## 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/uid1530107-20210408-1617864231352) 结果2：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1530107-20210408-1617864236930) 3-2.c 运行结果截图：结果1：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1530107-20210408-1617864240966) 结果2：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1530107-20210408-1617864245983) 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/uid1530107-20210408-1617864264856) 无折扣的运行结果：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1530107-20210408-1617864268922) 3-4.c 运行结果截图：结果1：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1530107-20210408-1617864276543) 结果2：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1530107-20210408-1617864283242) ### 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,b; printf("Please input a integer:"); scanf("%d",&a); b=fabs(a); printf("%d\n",b); return 0; } ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1530107-20210408-1617864310447) - -方法2的代码 ```c #include #include int main() { int a,b; printf("Please input a integer:"); scanf("%d",&a); if (a>=0) printf("%d\n",a); else { b=-a; printf("%d\n",b); } return 0; } ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1530107-20210408-1617864333871) 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() { char ch; scanf("%c",&ch); if ((ch>='0')&&(ch<='9')) printf("1"); else printf("0"); return 0; } ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1530107-20210408-1617864349871) ![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1530107-20210408-1617864355433) 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("Please input x:"); scanf("%d",&x); if (x<0) printf("0"); else if (x<10) printf("y=%d\n",x); else if (x<20) { y= x+1; printf("y=%d\n",y); } else if (x<30) { y= 2*x-1; printf("y=%d\n",y); } else { y= 3*x+1; printf("y=%d\n",y); } return 0; } ``` - 运行结果截图： ![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1530107-20210408-1617889783379) ![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1530107-20210408-1617889796193) - if嵌套方法实现的代码 ```c #include int main() { int x,y; printf("Please input x:"); scanf("%d",&x); if (x<30) if (x>=0) if (x>=10) if (x>=20) y=2*x-1; else y=x+1; else y=x; else y=0; else y=3*x+1; printf("%d\n",y); return 0; } ``` - 运行结果截图： ![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1530107-20210408-1617889807863) ![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1530107-20210408-1617889816120) ![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1530107-20210408-1617889822715) - 哪一种方法更好：各有所长，多分支法易于理解并且方便修改，嵌套法代码简洁字符数少 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 k; printf("Please input a number:"); scanf("%d",&k); if (k==1) printf("Monday:Green Vegetable "); else if (k==2) printf("Tuesday:Chicken "); else if (k==3) printf("Wednesday:Fish "); else if (k==4) printf("Thursday:Meet "); else if (k==5) printf("Friday:Egg "); else if (k==6) printf("Saterday:Bean Products "); else if (k==7) printf("Sunday:Seafood "); else printf("Error:Invalid input. "); return 0; } ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1530107-20210408-1617891668221) ![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1530107-20210408-1617891676190) - 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; printf("Please enter initial(capital):"); scanf("%c",&letter1); switch(letter1) { case 'S': getchar(); printf("Please enter the second letter(lower case):"); scanf("%c",&letter2); if (letter2=='a') printf("Saterday:Bean Products\n"); else if (letter2=='u') printf("Sunday:Seafood\n"); else printf("Error:Invalid input.\n"); break; case 'T': getchar(); printf("Please enter the second letter(lower case):"); scanf("%c",&letter2); if (letter2=='u') printf("Tuesday:Chicken\n"); else if (letter2=='h') printf("Thursday:Meet\n"); else printf("Error:Invalid input.\n"); break; case 'M': printf("Monday:Green Vegetable\n"); break; case 'W': printf("Wednesday:Fish\n"); break; case 'F': printf("Friday:Egg\n"); break; default: printf("Error:Invalid input.\n"); } return 0; } ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1530107-20210408-1617893866540) ![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1530107-20210408-1617893879802) ![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1530107-20210408-1617893891389)

“程序设计基础II”实验报告