## 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/uid1527846-20210408-1617861685754) 结果2：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1527846-20210408-1617862045217) ![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1527846-20210408-1617862074131) 3-2.c 运行结果截图：结果1：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1527846-20210408-1617862185006) 结果2：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1527846-20210408-1617862226530) 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/uid1527846-20210408-1617863275246) 无折扣的运行结果：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1527846-20210408-1617863993631) 3-4.c 运行结果截图：结果1：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1527846-20210408-1617864096580) 结果2：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1527846-20210408-1617864114273) ### 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; scanf ("%d", &a); printf("%f\n", fabs(a)); return 0; } ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1527846-20210411-1618122509267) - - 方法2的代码 ```c #include #include int main() { int a; scanf ("%d", &a); printf("%f\n", fabs(a)); return 0; } ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1527846-20210411-1618122657491) 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 c1,Y; printf("??????c1:"); scanf("%c",&c1); Y='c1'; printf("%d",Y); if(Y>0) printf("?1"); else printf("?0"); return 0; } ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1527846-20210411-1618122781804) 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() { 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); } ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1527846-20210411-1618122928323) - 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/uid1527846-20210411-1618122987251) - 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 a; printf("请输入a的数值:"); scanf("%d",&a); switch(a) { case 1:printf("男\n"); break; case 2:printf("女\n"); break; case 3:printf("老\n"); break; case 4:printf("少\n"); break; case 5:printf("大\n"); break; case 6:printf("小\n"); break; case 7:printf("中\n"); break; default :printf("error\n"); } return 0; } ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1527846-20210411-1618123233931)! - 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/uid1527846-20210411-1618123394892)

“程序设计基础II”实验报告