快速的方法来二进制数转换为十进制数 [英] Fast way to convert a binary number to a decimal number

问题描述

我要转换例如像 unsigned int类型bin_number = 10101010 成十进制再presentation（即 170 ）尽可能快地？最好的算法是什么？

I have to convert a binary number like for example unsigned int bin_number = 10101010 into its decimal representation (i.e. 170) as quickly as possible? What is the best algorithm?

推荐答案

使用模板，您可以在解决这个问题的编译时间的

Using templates you can solve this problem at compile-time.

template<unsigned long num>
struct binary
{
    static unsigned const value =
        binary<num/10>::value << 1 | num % 10;
};

// Specialization for zero
template<>
struct binary<0>
{ static unsigned const value = 0; };

二进制模板，再次用实例化一个较小的 NUM ，直到 NUM 达到零和专业化作为终止条件。

The binary template is instantiated again with a smaller num, until num reaches zero and the specialization is used as a termination condition.

例如：的std ::法院LT＆;＆LT;二进制＆LT; 10101010＆GT; ::值;

有关的运行时的问题：

unsigned binary_to_decimal(unsigned num)
{
    unsigned res = 0;

    for(int i = 0; num > 0; ++i)
    {
        if((num % 10) == 1)
            res += (1 << i);

        num /= 10;
    }

    return res;
}

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