## 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/uid1530027-20210411-1618131766099) 结果2： ![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1530027-20210411-1618131997828) 3-2.c 运行结果截图：结果1： ![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1530027-20210411-1618132407660) 结果2： ![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1530027-20210411-1618132455674) 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/uid1530027-20210411-1618133667513) 无折扣的运行结果： ![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1530027-20210411-1618133649277) 3-4.c 运行结果截图：结果1： ![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1530027-20210411-1618134417566) 结果2： ![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1530027-20210411-1618134458797) ### 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("请输入一个整数:"); scanf("%d",&a); b=fabs(a); printf("它的绝对值是:%d",b); return 0; } ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1530027-20210413-1618282626801) - - 方法2的代码 ```c #include #include int main() { int a,b; printf("请输入一个整数:"); scanf("%d",&a); printf("它的绝对值是:%d",b=fabs(a)); return 0; } ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1530027-20210413-1618282928386) 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 ch; printf("请输入一个字符"); scanf("%c",&ch); if(ch >= 'a' && ch <= 'z' || ch >= 'A' && ch <= 'Z'){ //字母的取值范围 printf("%c是一个字母\n",ch); }else if(ch >= '0' && ch <= '9'){ //数字的取值范围 printf("%c是一个数字\n",ch); }else{ printf("%c是一个特殊字符\n",ch); } return 0; } ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1530027-20210413-1618283364338) 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 enter the x:"); scanf("%d",&x); if(x<0) y=0; if(0<=x<10) y=x; if(10<=x<20) y=x+1; if(20<=x<30) y=2*x-1; if(30<=x) y=3*x+1; printf("x=%d,y=%d",x,y); return 0; } ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1530027-20210413-1618283829906) - if嵌套方法实现的代码 ```c #include int main() { int x,y; printf("Please enter the x:"); scanf("%d",&x); if(x<0) y=0; else { if(0<=x&&x<10) y=x; else { x=x; if(10<=x&&x<20) y=x+1; else { x=x; if(20<=x&&x<30) y=2*x-1; else { x=x; if(x>=30) y=3*x+1; } } } } printf("x=%d y=%d",x,y); return 0; } ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1530027-20210416-1618535644708) - 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 week,food; printf("What day is today?(Please enter the number:1-7)"); scanf("%d",week); switch(week) case 1: { printf("Monday: qingcai"); } case 2: { printf("Tuesday:ji"); } case 3: { printf("Wednesday:yu"); } case 4: { printf("Thursday:rou"); } case 5: { printf("Friday:jidan"); } case 6: { printf("Saturday:douzhipin"); } case 7: { printf("Sunday:haixian"); } default: { printf("The number is error"); } return 0; } ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1530027-20210416-1618537131875) - 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("Please enter the initial of the week: "); ch=getchar(); getchar(); switch(ch) { case 'M': printf("Today is Monday. "); break; case 'T': printf("Please enter the second letter of the week: "); ch2=getchar(); getchar(); if(ch2=='u') printf("Today is Tuesday. "); else if(ch2=='h') printf("Today is Thursday. "); else printf("You enter's letter is error."); break; case 'W': printf("Today is Wednesday. "); break; case 'F': printf("Today is Friday. "); break; case 'S': printf("Please enter the second letter of the week: "); ch2=getchar(); getchar(); if(ch2=='a') printf("Today is Saturday. "); else if(ch2=='u') printf("Today is Sunday. "); else printf("You enter's letter is error."); break; default: printf("You enter's letter is error."); break; } return 0; } ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1530027-20210416-1618538497467)

“程序设计基础II”实验报告