判断一个整数的二进制表示中，第i位是否为1

check.cpp内容如下：

#include <iostream>
using namespace std;

// check if the i-th bit is set or not in the binary form of n.
bool check(int n, int i)
{
    if (n & (1 << i))
        return true;
    return false;
}

int main(int argc, char **argv)
{
    const int kRange = 20;
    for (int i = 0; i < kRange; ++i)
        if (check(i, 3))
            cout << "The 3rd bit is set in the binary form of " << i << endl;

    return 0;
}

运行结果如下图：