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QOJ
ID | Problem | Submitter | Result | Time | Memory | Language | File size | Submit time | Judge time |
---|---|---|---|---|---|---|---|---|---|
#350637 | #6736. Alice and Bob | Albert711 | RE | 0ms | 0kb | C++20 | 1.6kb | 2024-03-10 22:24:48 | 2024-03-10 22:24:48 |
answer
#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef double db;
const int N = 1e7 + 5;
const int mod = 998244353;
//#define int long long
using i64 = int64_t;
std::bitset<N> bt[N];
i64 fpow(i64 x, i64 r) {
i64 result = 1;
while (r) {
if (r & 1)result = result * x % mod;
r >>= 1;
x = x * x % mod;
}
return result;
}
namespace binom {
i64 fac[N], ifac[N];
int __ = [] {
fac[0] = 1;
for (int i = 1; i <= N - 5; i++)
fac[i] = fac[i - 1] * i % mod;
ifac[N - 5] = fpow(fac[N - 5], mod - 2);
for (int i = N - 5; i; i--)
ifac[i - 1] = ifac[i] * i % mod;
return 0;
}();
inline i64 C(int n, int m) {
if (n < m || m < 0)return 0;
return fac[n] * ifac[m] % mod * ifac[n - m] % mod;
}
inline i64 A(int n, int m) {
if (n < m || m < 0)return 0;
return fac[n] * ifac[n - m] % mod;
}
}
using namespace binom;
void solve() {
ll n;
cin >> n;
if(n==1) {
cout<<1<<'\n';return;
}
ll ans = 0;
ll tmp = 1;
for (int i = 1; i <= n - 1; i++) tmp = tmp * i % mod;
ll tt = tmp;
for (int i = 1; i <= n; i++) {
if (i - 1 > n - i) break;
ans = ans + A(n - i, i - 1) * tt % mod;
ans %= mod;
tt = tt * fpow(n - i, mod - 2) % mod;
}
cout << ans << '\n';
}
signed main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
cout.tie(nullptr);
// cout << fixed << setprecision(1);
int T = 1;
// cin >> T;
while (T--) solve();
return 0;
}
Details
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Test #1:
score: 0
Runtime Error
input:
1