エラトステネスで素因数分解

prime.rb

puts "xを素因数分解します。"

while true
  print " x > "
  x = gets.to_i #上限
  if x >= 1
    break
  end
end

a = []
for i in 2..x
a << i
end


k = 0 
while k < Math.sqrt(x) 
  i = 1   
  while i < a.length  
    if a[i] % a[k] == 0 && i != k    
      a.delete_at i
    end
    i += 1
  end
  k += 1
end

print x.to_s + " = 1"
for i in 0..(a.length-1)
  count = 0
  while true
    if (x % a[i]) == 0
      x = x / a[i]
      count += 1
      next
    end
    if count > 1
      print " * " + a[i].to_s + "^" + count.to_s
    elsif count == 1
      print " * " + a[i].to_s
    end
    break
  end
end

前回投稿の篩を使っただけ