一个很简单的程序代码,小弟不懂,望高手指教
#include <iostream.h>
void main()
{
int a;
cout <<"please input a number:\n";
cin >>a;
int c1 = a%3 ==0;
int c2 = a%5 ==0;
int c3 = a%7 ==0;
switch((c1<<2)+(c2<<1)+c3){
case 0: cout <<"不能被3,5,7整除.\n"; break;
case 1: cout <<"只能被7整除.\n"; break;
case 2: cout <<"只能被5整除.\n"; break;
case 3: cout <<"可以被5,7整除.\n"; break;
case 4: cout <<"只能被3整除.\n"; break;
case 5: cout <<"可以被3,7整除.\n"; break;
case 6: cout <<"可以被3,5整除.\n"; break;
case 7: cout <<"可以被3,5,7整除.\n"; break;
}
}
就是这句不懂switch((c1<<2)+(c2<<1)+c3)
参考答案:c1<<2
的值为c1 * 2*2;
故：
witch((c1<<2)+(c2<<1)+c3)
即：
witch(c1*2*2+c2*2+c3)