一道整除的问题
#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; } } 这是一个关于整除的问题,有两个地方看不懂 1. int c1 = a%3 ==0;//这里为什么还要弄个==0,好像加不加无所谓嘛 2. switch((c1<<2)+(c2<<1)+c3)//挂号里的c1<<2表示什么意思?
