从char *到二进制的十进制

Question

I have a string that consists some decimal value, with number of digits can be more than any existing int-types can hold(I know the number of digits). Give me some hints, please, how can I convert that number to it's binary representation (so I will have other char* variable, that will consist binary).

Answer 1

您可以使用类似GNU Multiple Precision库的东西，它支持很长的数字。

Answer 2

You'll need a custom BigInt library. GMP would be a good choice.

Answer 3

Just some hints (if you want to implement it by hand).

I did that (homework) this way:

1. I used an array of unsigned int to store the bit representing the number(using two's complement representation).
2. I implemented shift and addition operations on that array (with the same semantic of classical integrals type).
3. Since you can express a number with sum of products I used an algorithm with shift and add(like shown on this post ). You can use the position of a single character in the string to generate the right binary representation.

(I don't know if there are better or faster solutions.) I won't post the code, this way you can enjoy to do it yourself ;)