Problem 4 - Project Euler

#start_time = Time::now
val = 0
for i in 900..999
    for j in 900..999
        num = i * j
        n = num.to_s
        val = num if (n.slice(0,1) == n.slice(5,1))&&(n.slice(1,1) == n.slice(4,1))&&(n.slice(2,1) == n.slice(3,1))&&(num > val)
    end
end

puts val
#end_time = Time::now
#puts end_time - start_time

最初に解いたときは val = num if (n.slice(0,1) == n.slice(5,1))&&(n.slice(1,1) == n.slice(4,1))&&(n.slice(2,1) == n.slice(3,1))&&(num > val) の部分が多重ネストになってたのだが，うざかったので1本にまとめた．