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AtCoder Beginner Contest 169, D. Div Game の短めのコード

Last updated at Posted at 2020-06-05

「$p^1, p^2, p^3, \ldots$ で割っていって割れた回数を記録し、
回数の記録を中止して$p$で割れるだけ割っておく」
を $p = 2, 3, 5, 7, 9, \ldots , \sqrt{N}$ で繰り返す。
素数がまだ残っているなら 1 を足す。
みたいな。

N = int(input())
n, p, score = N, 2, 0
while p ** 2 <= N:
  e = 1
  while n % (p ** e) == 0:
    n //= (p ** e)
    score += 1
    e += 1
  else:
    while n % p == 0:
      n //= p
    p = p + 1 if p == 2 else p + 2
else:
  if n != 1:
    score += 1
print(score)

もう少しだけ短く

N = int(input())
n, p, score = N, 2, 0
while p ** 2 <= N:
  e = 1
  while n % (p ** e) == 0:
    n //= (p ** e)
    score += 1
    e += 1
  else:
    while n % p == 0:
      n //= p
    p += 2 - (p == 2)
else:
  score += n > 1
print(score)
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