## 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/uid1535329-20210413-1618318685467) 结果2：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1535329-20210413-1618318719228) 3-2.c 运行结果截图：结果1： ![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1535329-20210413-1618318884639) 结果2： ![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1535329-20210413-1618318920948) 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/uid1535329-20210413-1618319165099) 无折扣的运行结果：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1535329-20210413-1618319129411) 3-4.c 运行结果截图：结果1：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1535329-20210413-1618319326575) 结果2：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1535329-20210413-1618319388459) ### 上机练习 1、输入一个整数，输出它的绝对值。 # include #include int main( ) { int a,b; printf("input a int:"); scanf("%d",&a); b = fabs(a); printf("it is :%d",b); return 0; } - 运行结果截图： - ![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1535329-20210414-1618407109252) - 方法2的代码 # include #include int main( ) { int a,b; printf("input a int:"); scanf("%d",&a); if(a>=0) printf("it is:%d",a); else { b = -a; printf("it is :%d",b); } return 0; } ``` - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1535329-20210414-1618407401430) 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。 # include #include int main( ) { char a; printf("shu ru yi ge zifu:"); scanf("%c",&a); if(a<65) printf("%d",a<65); else printf("%d",a<65); return 0; } - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1535329-20210414-1618407491866) 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 a,b; printf("input X:"); scanf("%d",&a); if(a<0) { b=0; printf("X = %d,Y = %d",a,b); } else if(a<10) { b=a; printf("X = %d,Y = %d",a,b); } else if(a<20) { b = a +1; printf("X = %d,Y = %d",a,b);} else if(a<30) { b= 2*a-1; printf("X = %d,Y = %d",a,b);} else { b = 3*a+1; printf("X = %d,Y = %d",a,b); } return 0; } - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1535329-20210414-1618407733830) - if嵌套方法实现的代码 # include int main( ) { int x,y; printf("input X:"); scanf("%d",&x); if(x<0) y = 0; else { if(x<10) y=x; else { if(x<20) y=x+1; else{ if(x<30) y=2*x-1; else{ 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/uid1535329-20210414-1618409506652) - 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 # include int main() { int a; printf("input 1-7,show menu:"); scanf("%d",&a); switch (a) {case 1:printf("?????? "); break; case 2:printf("????? "); break; case 3:printf("????? "); break; case 4:printf("????? "); break; case 5:printf("?????? "); break; case 6:printf("??????? "); break; case 7:printf("?????? "); break; } - 运行结果截图：![图片描述](https://dn-simplecloud.shiyanlou.com/courses/uid1535329-20210414-1618409740915) - 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 #将修改后代码填在此处，然后删除这行文字 ``` - 运行结果截图：

“程序设计基础II”实验报告