《Cracking the Coding Interview》——第5章：位操作——题目6

2014-03-19 06:24

题目：将一个整数的奇偶二进制位交换，(0, 1) (2, 3) ...

解法：使用掩码来进行快速交换，定义掩码为'0101...'和‘1010...’。

代码：

// 5.6 Swap odd and even bits in an integer.
#include <cstdio>
using namespace std;

unsigned int swapBits(unsigned int n)
{
    static const unsigned int mask[2] = {0x55555555, 0xaaaaaaaa};
    
    return ((n & mask[0]) << 1) + ((n & mask[1]) >> 1);
}

int main()
{
    unsigned int n;
    
    while (scanf("%u", &n) == 1) {
        printf("%u\n", swapBits(n));
    }
    
    return 0;
}