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QOJ

IDProblemSubmitterResultTimeMemoryLanguageFile sizeSubmit timeJudge time
#619838#8635. 圆zfs732100 ✓51ms101120kbC++142.3kb2024-10-07 15:35:222024-10-07 15:35:22

Judging History

你现在查看的是最新测评结果

  • [2024-10-07 15:35:22]
  • 评测
  • 测评结果:100
  • 用时:51ms
  • 内存:101120kb
  • [2024-10-07 15:35:22]
  • 提交

answer

/*
* _|_|_|_|_|  _|_|_|_|    _|_|_|  _|_|_|_|_|  _|_|_|      _|_|
 *       _|    _|        _|                _|        _|  _|    _|
 *     _|      _|_|_|      _|_|          _|      _|_|        _|
 *   _|        _|              _|      _|            _|    _|
 * _|_|_|_|_|  _|        _|_|_|      _|        _|_|_|    _|_|_|_|
 */

#include <bits/stdc++.h>

constexpr int pMod = 998244353;

template<class Tp>
Tp Add(Tp x) {
  return x;
}

template<class Tp>
Tp Mul(Tp x) {
  return x;
}

template<class Tp, class... Tps>
int Add(Tp x, Tps... y) {
  return (x + Add(y...)) % pMod;
}

template<class Tp, class... Tps>
int Mul(Tp x, Tps... y) {
  return int(1LL * x * Mul(y...) % pMod);
}

template<class Tp, class... Tps>
void AddC(Tp &x, Tps... y) {
  x = Add(x, y...);
}

template<class Tp, class... Tps>
void MulC(Tp &x, Tps... y) {
  x = Mul(x, y...);
}

int ExGcd(int a, int b, int &x, int &y) {
  if (b == 0) return x = 1, y = 0, a;
  int d = ExGcd(b, a % b, y, x);
  return y -= a / b * x, d;
}

int Inv(int x) {
  int ret, t, d = ExGcd(x, pMod, ret, t);
  return d * Add(ret, pMod);
}

std::vector<int> fac, invFac;

void InitFac(int n) {
  fac.resize(n + 1);
  invFac.resize(n + 1);
  fac[0] = 1;
  for (int i = 1; i <= n; i++) fac[i] = Mul(fac[i - 1], i);
  invFac[n] = Inv(fac[n]);
  for (int i = n; i >= 1; i--) invFac[i - 1] = Mul(invFac[i], i);
}

namespace Solution {
  int Solve(int N) {
    if (N == 3) {
      return 1;
    }

    InitFac(N);
    int ans = 0;

    std::vector<std::vector<int>> dp(N, std::vector<int>(N));
    dp[1][1] = 1;

    for (int i = 1; i + 2 < N; i++) {
      for (int j = 1; j <= i; j++) {
        for (int k = 1; k <= 3; k++) {
          if (i + k + 2 < N) {
            AddC(dp[i + k][j + 1], dp[i][j]);
          }
        }
      }
    }

    for (int l = 0; l < 3; l++) {
      int p = N - 3 - l;
      if (p <= 0) {
        continue;
      }
      for (int j = 1; j <= p; j++) {
        int v = Mul(dp[p][j], fac[j]);
        MulC(v, invFac[N], fac[N - j - 1]);
        AddC(ans, Mul(v, 3 - l, j + 1));
      }
    }

    return Mul(ans, N);
  }
}

int main() {
  std::ios::sync_with_stdio(false);
  std::cin.tie(nullptr);

  int N;
  std::cin >> N;
  std::cout << Solution::Solve(N) << '\n';

  return 0;
}

Details

Tip: Click on the bar to expand more detailed information

Pretests


Final Tests

Test #1:

score: 10
Accepted
time: 0ms
memory: 3616kb

input:

3

output:

1

result:

ok 1 number(s): "1"

Test #2:

score: 10
Accepted
time: 0ms
memory: 3616kb

input:

4

output:

2

result:

ok 1 number(s): "2"

Test #3:

score: 10
Accepted
time: 0ms
memory: 3608kb

input:

6

output:

299473309

result:

ok 1 number(s): "299473309"

Test #4:

score: 10
Accepted
time: 0ms
memory: 3644kb

input:

10

output:

487238321

result:

ok 1 number(s): "487238321"

Test #5:

score: 10
Accepted
time: 0ms
memory: 3652kb

input:

100

output:

41620761

result:

ok 1 number(s): "41620761"

Test #6:

score: 10
Accepted
time: 1ms
memory: 3632kb

input:

200

output:

208771764

result:

ok 1 number(s): "208771764"

Test #7:

score: 10
Accepted
time: 1ms
memory: 4108kb

input:

500

output:

888621375

result:

ok 1 number(s): "888621375"

Test #8:

score: 10
Accepted
time: 47ms
memory: 93336kb

input:

4798

output:

319137015

result:

ok 1 number(s): "319137015"

Test #9:

score: 10
Accepted
time: 51ms
memory: 101000kb

input:

4999

output:

818467659

result:

ok 1 number(s): "818467659"

Test #10:

score: 10
Accepted
time: 49ms
memory: 101120kb

input:

5000

output:

142907477

result:

ok 1 number(s): "142907477"