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ID题目提交者结果用时内存语言文件大小提交时间测评时间
#588792#6417. Classical Summation ProblemTobo#WA 0ms3856kbC++202.8kb2024-09-25 14:34:252024-09-25 14:34:26

Judging History

你现在查看的是最新测评结果

  • [2024-09-25 14:34:26]
  • 评测
  • 测评结果:WA
  • 用时:0ms
  • 内存:3856kb
  • [2024-09-25 14:34:25]
  • 提交

answer

#include <bits/stdc++.h>
using namespace std;

template <int mod>
unsigned int down(unsigned int x)
{
    return x >= mod ? x - mod : x;
}
template <int mod>
struct Modint
{
    unsigned int x;
    Modint() = default;
    Modint(unsigned int x) : x(x) {}
    friend istream &operator>>(istream &in, Modint &a) { return in >> a.x; }
    friend ostream &operator<<(ostream &out, Modint a) { return out << a.x; }
    friend Modint operator+(Modint a, Modint b) { return down<mod>(a.x + b.x); }
    friend Modint operator-(Modint a, Modint b) { return down<mod>(a.x - b.x + mod); }
    friend Modint operator*(Modint a, Modint b) { return 1ULL * a.x * b.x % mod; }
    friend Modint operator/(Modint a, Modint b) { return a * ~b; }
    friend Modint operator^(Modint a, int b)
    {
        Modint ans = 1;
        for (; b; b >>= 1, a *= a)
            if (b & 1)
                ans *= a;
        return ans;
    }
    friend Modint operator~(Modint a) { return a ^ (mod - 2); }
    friend Modint operator-(Modint a) { return down<mod>(mod - a.x); }
    friend Modint &operator+=(Modint &a, Modint b) { return a = a + b; }
    friend Modint &operator-=(Modint &a, Modint b) { return a = a - b; }
    friend Modint &operator*=(Modint &a, Modint b) { return a = a * b; }
    friend Modint &operator/=(Modint &a, Modint b) { return a = a / b; }
    friend Modint &operator^=(Modint &a, int b) { return a = a ^ b; }
    friend Modint &operator++(Modint &a) { return a += 1; }
    friend Modint operator++(Modint &a, int)
    {
        Modint x = a;
        a += 1;
        return x;
    }
    friend Modint &operator--(Modint &a) { return a -= 1; }
    friend Modint operator--(Modint &a, int)
    {
        Modint x = a;
        a -= 1;
        return x;
    }
    friend bool operator==(Modint a, Modint b) { return a.x == b.x; }
    friend bool operator!=(Modint a, Modint b) { return !(a == b); }
};
const int mod = 998244353;
typedef Modint<mod> mint;

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

    int n, k;
    cin >> n >> k;

    if (k & 1)
    {
        mint ans = mint(n) ^ k;
        ans *= (n + 1);
        ans /= 2;
        cout << ans << '\n';
        exit(0);
    }

    vector<mint> fac(n + 1), ifac(n + 1);
    fac[0] = ifac[0] = 1;
    for (int i = 1; i <= n; i++)
    {
        fac[i] = fac[i - 1] * i;
        ifac[i] = mint(1) / fac[i];
    }
    auto binom = [&](int x, int y) -> mint
    {
        return fac[x] * ifac[y] * ifac[x - y];
    };

    mint sum = 0;
    for (int i = 2; i <= n; i++)
    {
        mint tmp = binom(k, k / 2);
        tmp *= mint(i - 1) ^ (k / 2);
        tmp *= mint(n - i + 1) ^ (k / 2);
        sum -= tmp;
    }
    sum /= mint(n) ^ k;
    sum += n + 1;
    sum /= 2;
    sum *= mint(n) ^ k;
    cout << sum << '\n';
}

详细

Test #1:

score: 100
Accepted
time: 0ms
memory: 3856kb

input:

3 2

output:

14

result:

ok 1 number(s): "14"

Test #2:

score: 0
Accepted
time: 0ms
memory: 3560kb

input:

5 3

output:

375

result:

ok 1 number(s): "375"

Test #3:

score: 0
Accepted
time: 0ms
memory: 3848kb

input:

2 2

output:

5

result:

ok 1 number(s): "5"

Test #4:

score: 0
Accepted
time: 0ms
memory: 3560kb

input:

10 9

output:

508778235

result:

ok 1 number(s): "508778235"

Test #5:

score: 0
Accepted
time: 0ms
memory: 3572kb

input:

69 3

output:

11497815

result:

ok 1 number(s): "11497815"

Test #6:

score: 0
Accepted
time: 0ms
memory: 3624kb

input:

994 515

output:

33689623

result:

ok 1 number(s): "33689623"

Test #7:

score: -100
Wrong Answer
time: 0ms
memory: 3592kb

input:

4476 6182

output:

314699348

result:

wrong answer 1st numbers differ - expected: '114894183', found: '314699348'