## 实验3 选择结构程序设计 ### 实验任务 3-1.c 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1532864-20210411-1618139221408) 结果1：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1532864-20210411-1618139659217) 结果2：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1532864-20210411-1618139696526) 3-2.c 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1532864-20210412-1618185977543) 结果1：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1532864-20210412-1618185962685) 结果2：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1532864-20210412-1618186007936) 3-3.c 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1532864-20210412-1618189095798) 有折扣的运行结果：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1532864-20210412-1618189203987) 无折扣的运行结果：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1532864-20210412-1618189180553) 3-4.c 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1532864-20210412-1618190552959) 结果1：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1532864-20210412-1618190788024) 结果2：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1532864-20210412-1618190837814) ### 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 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/uid1532864-20210412-1618221193796) - - 方法2的代码 ```c #include int main() { int x; scanf("%d",&x); if(x>=0) printf("%d",x); else { x=x*(-1); printf("%d",x); } return 0; } ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1532864-20210413-1618270569368) 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 num; scanf("%c",&num); if(isdigit(num)==0) { printf("0"); } else { printf("1"); } return 0; } ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1532864-20210413-1618271118070) 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 #include int main() { char num; scanf("%c",&num); if(isdigit(num)==0) { printf("0"); } else { printf("1"); } return 0; } ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1532864-20210413-1618273058825) - if嵌套方法实现的代码 ```c #include #include int main() { int x, y; printf("Please input x:"); scanf("%d", &x); if (x < 0) y = 0; if (x >= 0 && x < 10) { y = x; } if (x >= 10 && x < 20) { y = x + 1; } if (x >= 20 && x <30) {y = 2 * x - 1; } if (x >=30) { y = 3 * + 1; } printf("y: %d", y); return 0; } ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1532864-20210413-1618274238059) - 哪一种方法更好：方法一 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 #include int main() { int x; printf("Please input (1-7)x :"); scanf("%d", &x); switch(x) { case 1: printf("Monday :qincai"); 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("Sunday :haixian"); break; } return 0; } ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1532864-20210413-1618276329394) - 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 day,sd; printf("????????:"); scanf("%c",&day); getchar(); switch(day) { case 'M':printf("?? ");break; case 'T': {printf("????????:"); scanf("%c",&sd); switch(sd) { case 'u':printf("? ");break; case 'h':printf("? ");break; } break;} case 'W':printf("? ");break; case 'F':printf("?? ");break; case 'S': {printf("????????:"); scanf("%c",&sd); switch(sd) { case 'a':printf("??? ");break; case 'u':printf("?? ");break; } break;} default:printf("???? "); } return 0; } ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1532864-20210413-1618277885526)

“程序设计基础II”实验报告