Take the number 192 and multiply it by each of 1, 2, and 3:
192 1 = 192
192 2 = 384
192 3 = 576
By concatenating each product we get the 1 to 9 pandigital, 192384576. We will call 192384576 the concatenated product of 192 and (1,2,3)
The same can be achieved by starting with 9 and multiplying by 1, 2, 3, 4, and 5, giving the pandigital, 918273645, which is the concatenated product of 9 and (1,2,3,4,5).
What is the largest 1 to 9 pandigital 9-digit number that can be formed as the concatenated product of an integer with (1,2, ... , n) where n 1?
def p38_check(n) str=n.to_s i=1 str+=(n*(i+=1)).to_s while(str.length<9) return false if(str.length>9) return false unless str.split("").sort.join("")=="123456789" return str.to_i end def p38 largest=0 (2...10000).each do |i| if jake=p38_check(i) largest=jake if jake>largest end end puts largest end