## 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/uid1528819-20210408-1617875247754) 结果2：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1528819-20210408-1617875619268) 3-2.c 运行结果截图：结果1：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1528819-20210408-1617876167567) 结果2：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1528819-20210408-1617876193718) 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/uid1528819-20210408-1617876908250) 无折扣的运行结果：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1528819-20210408-1617876976368) 3-4.c 运行结果截图：结果1：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1528819-20210414-1618408598394) 结果2：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1528819-20210414-1618408622960) ### 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 int main() { int a,b; printf("Please input a,b for a triangler:"); scanf("%d\n",b); b = abs(a); printf("%d\n",b); return 0; } ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1528819-20210414-1618409738216) - - 方法2的代码 ```c int main() { int a,b; printf("Please input a for a triangle:"); scanf("%d",&a); b=-a; if(a<=0) { printf("%d,b"); } else printf("%d,a"); return 0; } ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1528819-20210414-1618411109714) 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 int main() { int a; printf("Please input a for a this"); scanf("%d",&a); if(a!=num) { printf("%d",0); } else printf("%d",1); return 0; } ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1528819-20210414-1618411777466) ![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1528819-20210414-1618412232922) 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 int main() { int x,y; printf("Please input a for a x:"); scanf("%d",&x); if(x<0)y=0; else if(x>=0 && x<10)y=x; else if(x>=10 && x<20)y=x+1; else if(x>=20 && x<30)y=2*x-1; else if(x>=30)y=3*x+1; printf("y=%d",y); return 0; } ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1528819-20210414-1618413127866) - if嵌套方法实现的代码 ```c int main() { int x,y; printf("Please input a for a x:"); scanf("%d",&x); if(x<0)y=0; else (x>=0 && x<10)y=x; { if(x>=10 && x<20)y=x+1; else if(x>=20 && x<30)y=2*x-1; else if(x>=30)y=3*x+1; } printf("y=%d",y); return 0; } ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1528819-20210414-1618413716050) - 哪一种方法更好：第一个 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 int main() { int date; printf("please input an interger(1-7):"); scanf("%d",&date); switch(date) { case 1: printf("青菜"); break; case 2: printf("鸡"); break; case 3: printf("鱼"); break; case 4: printf("肉"); break; case 5: printf("鸡蛋"); break; case 6: printf("豆制品"); break; case 7: printf("海鲜"); break; return 0; } } ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1528819-20210414-1618415148965) - 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( ) { int date; double value1, value2; printf("shuruxingqiji:"); scanf("%d", &date); switch(date) { case 'm': printf("jintianxingqiyi,chiqingcai"); break; case 'tu': printf("jintianxingqier,chiji"); break; case 'w': printf("jintianxqisan,chiyu"); break; case 'ts': printf("jintisnxingqisi,chirou"); break; case 'f': printf("jintianxingqiwu,chijidan"); break; case 'st': printf("jintianxingqiliu,chidouzhiping"); break; case 'su': printf("jintianxingqiri,chihaixian"); break; default: printf("Unknown operator"); break; } return 0; } ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1528819-20210414-1618415617214)

“程序设计基础II”实验报告