2017-11-08 17:39:50 +01:00
This is effectively an optimized implementation of [this algorithm ](http://www.mathblog.dk/project-euler-51-eight-prime-family/ ).
You can see the ten patterns on the left side and beside them the area were we build our numbers.
So what we do is iterate through the numbers from `100` to `1 000` , through the ten patterns and through the digits `0` , `1` and `2` .
2018-02-03 16:50:58 +01:00
In each iteration we generate the number (from value, pattern and digit) and test for it primeness (with a simple [primality test ](https://en.wikipedia.org/wiki/Primality_test ) - no prime sieve).
2017-11-08 17:39:50 +01:00
If we found a prime we count the number of primes in it's family and if this count is eight we print the generated number and exit.
This program is not the fastest, because I check all the primes "manually" and not with an prime sieve each iteration takes quite a time.
But I wanted this to fit into the befunge-93 size restrictions, and even without a sieve the execution time is OK - for a befunge program.
