Submission #71156128

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Source Code Expand

mod = 998244353

S = list(map(int, input().strip()))
n = len(S)

fact = [1] * (n + 1)
for i in range(1, n + 1):
  fact[i] = fact[i - 1] * i % mod

invfact = [1] * (n + 1)
invfact[n] = pow(fact[n], mod - 2, mod)
for i in range(n, 0, -1):
  invfact[i - 1] = invfact[i] * i % mod

def comb(a, b):
  if b < 0 or b > a:
    return 0
  return fact[a] * invfact[b] % mod * invfact[a - b] % mod

right = [0] * 10
for s in S:
  right[s] += 1

ans = 0
left = [0] * 10
for s in S:
  right[s] -= 1
  if s != 9:
    L = left[s]
    R = right[s + 1]
    if R > 0:
      ans += comb(L + R, R - 1)
      ans %= mod
  left[s] += 1
  # print(s, ans)

print(ans)

Submission Info

Judge Result