project-euler/Sidef/036 Double-base palindromes -- v2.sf

#!/usr/bin/ruby

# Daniel "Trizen" Șuteu
# Date: 09 October 2017
# https://github.com/trizen

# https://projecteuler.net/problem=36

# Runtime: 0.320s

var sum = 0
var limit = 1e6

for k in (0 .. limit.log2.ceil>>1) {
    [0,1].variations_with_repetition(k, {|*a|

        next if a[0]==0

        for b in (['', '0', '1']) {
            with (Num(a.join + b + a.join.flip, 2)) { |n|
                if (n<limit && Str(n)==Str(n).flip) {
                    sum += n
                }
            }
        }
    })
}

say sum