27 lines
832 B
Markdown
27 lines
832 B
Markdown
|
A short look to [Wikipedia](https://en.wikipedia.org/wiki/Methods_of_computing_square_roots#Digit-by-digit_calculation) finds us a neat algorithm to calculate the square-root digit-by-digit.
|
||
|
|
|
||
|
|
I have optimized it a little bit with the target to use not so many variables:
|
||
|
|
|
||
|
|
~~~
|
||
|
|
IEnumerable<int> DRoot(int r)
|
||
|
|
{
|
||
|
|
BigInteger c = r;
|
||
|
|
BigInteger p = 0;
|
||
|
|
int x = 0;
|
||
|
|
|
||
|
|
for (ii = 0; ii < 100; ii++)
|
||
|
|
{
|
||
|
|
for (x = 0;(x+1)*(20*p + (x+1)) <= c;x++);
|
||
|
|
c = 100*c - 2000*p*x - 100*x*x;
|
||
|
|
p = p*10 + x;
|
||
|
|
}
|
||
|
|
|
||
|
|
return p;
|
||
|
|
}
|
||
|
|
~~~
|
||
|
|
|
||
|
|
The algorithm is pretty simple, but *god* do I hate long addition/multiplication in Befunge.
|
||
|
|
|
||
|
|
We need 120 base-10 digits for the numbers `p`and `c`.
|
||
|
|
In our program we use base-100 notation. This way we can fit the numbers in a single befunge-93 row
|
||
|
|
**and** can simply multiply by 100 with a single left shift operation.
|