移位运算

#include <cstdio>
#include <iostream>
using namespace std;
int main()
{
    int i=3;
    int a=i<<1; //3*2^1
    int b=i<<2; //3*2^2
    int c=1<<i; //1*2^3
    int d=2<<i; //2*2^3
    //a<<b  ==  a*2^b;
    cout<<a<<endl<<b<<endl<<c<<endl<<d<<endl;
    return 0;
}