プログラミングコンテストの問題

dame.rb

#ダメ解答

f = 1
s = 0

for i in 1..100 do
  f *= i
end

n = f

for i in 0..Math.log10(f).floor do
  n,b = n.divmod(10)
  s+= b
end

puts s

mohan.rb

#模範解答

f = 1
fs = ""
s = 0

for i in 1..100 do
  f *= i
end

fs = f.to_s

for i in 0 .. fs.length - 1 do
  s += fs[i,1].to_i  
end

puts s