在二进制数算出尾随0 [英] Finding trailing 0s in a binary number

问题描述

如何找到一个二进制数基于K＆放尾0的号码;？在二进制数发现1S中的R位计数比如我修改它了一下，找到尾随0

How to find number of trailing 0s in a binary number?Based on K&R bitcount example of finding 1s in a binary number i modified it a bit to find the trailing 0s.

int bitcount(unsigned x)
{
  int b;
  for(b=0;x!=0;x>>=1)
      {
        if(x&01)
          break;
        else
          b++;
      }

我想回顾一下这个方法。

I would like to review this method.

推荐答案

下面的计算并行的计数而提高效率的一种方式：

Here's a way to compute the count in parallel for better efficiency:

unsigned int v;      // 32-bit word input to count zero bits on right
unsigned int c = 32; // c will be the number of zero bits on the right
v &= -signed(v);
if (v) c--;
if (v & 0x0000FFFF) c -= 16;
if (v & 0x00FF00FF) c -= 8;
if (v & 0x0F0F0F0F) c -= 4;
if (v & 0x33333333) c -= 2;
if (v & 0x55555555) c -= 1;

这篇关于在二进制数算出尾随0的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！