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General

# Author Problem Lang Verdict Time Memory Sent Judged
86411748 Practice:
JKLover
960G - 18 GNU C++17 Accepted 608 ms 9184 KB 2020-07-10 11:56:12 2020-07-10 11:56:12

→ Source
//%std
#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
{
int out = 0, fh = 1;
char jp = getchar();
while ((jp > '9' || jp < '0') && jp != '-')
jp = getchar();
if (jp == '-')
fh = -1, jp = getchar();
while (jp >= '0' && jp <= '9')
out = out * 10 + jp - '0', jp = getchar();
return out * fh;
}
void print(int x)
{
if (x >= 10)
print(x / 10);
putchar('0' + x % 10);
}
void write(int x, char c)
{
if (x < 0)
putchar('-'), x = -x;
print(x);
putchar(c);
}
const int P = 998244353, G = 3;
{
return a + b >= P ? a + b - P : a + b;
}
void inc(int &a, int b)
{
}
int mul(int a, int b)
{
return 1LL * a * b % P;
}
int fpow(int a, int b)
{
int res = 1;
while (b)
{
if (b & 1)
res = mul(res, a);
a = mul(a, a);
b >>= 1;
}
return res;
}
const int N = 1 << 17 | 10;
int curn = 0, invn, rev[N], omega[N], inv[N];
void init(int n)
{
if (n == curn)
return;
invn = fpow(n, P - 2);
for (int i = 0; i < n; ++i)
rev[i] = (rev[i >> 1] >> 1) | ((i & 1) * (n >> 1));
for (int l = 2; l <= n; l <<= 1)
{
omega[l] = fpow(G, (P - 1) / l);
inv[l] = fpow(omega[l], P - 2);
}
curn = n;
}
void DFT(int *a, int n, bool invflag)
{
init(n);
for (int i = 0; i < n; ++i)
if (i < rev[i])
swap(a[i], a[rev[i]]);
for (int l = 2; l <= n; l <<= 1)
{
int gi = omega[l], m = l >> 1;
if (invflag)
gi = inv[l];
for (int *p = a; p != a + n; p += l)
{
int g = 1;
for (int i = 0; i < m; ++i)
{
int t = mul(g, p[i + m]);
p[i + m] = add(p[i], P - t);
g = mul(g, gi);
}
}
}
if (invflag)
{
for (int i = 0; i < n; ++i)
a[i] = mul(a[i], invn);
}
}
typedef vector<int> poly;
int _a[N], _b[N], _c[N];
poly operator * (const poly &A, const poly &B)
{
int len = A.size() + B.size() - 1, n = 1;
poly C(len);
while (n < len)
n <<= 1;
int lenA = A.size(), lenB = B.size();
for (int i = 0; i < lenA; ++i)
_a[i] = A[i];
for (int i = lenA; i < n; ++i)
_a[i] = 0;
for (int i = 0; i < lenB; ++i)
_b[i] = B[i];
for (int i = lenB; i < n; ++i)
_b[i] = 0;
DFT(_a, n, false);
DFT(_b, n, false);
for (int i = 0; i < n; ++i)
_c[i] = mul(_a[i], _b[i]);
DFT(_c, n, true);
for (int i = 0; i < len; ++i)
C[i] = _c[i];
return C;
}
int n, m, fac[N], invfac[N], A, B;
poly Prod(int l, int r)
{
if (l == r)
return poly{l, 1};
int mid = (l + r) >> 1;
return Prod(l, mid) * Prod(mid + 1, r);
}
int binom(int x, int y)
{
return mul(fac[x], mul(invfac[y], invfac[x - y]));
}
int main()
{
if (A < 0 || B < 0 || A + B > n - 1)
return puts("0"), 0;
if (n == 1)
return puts("1"), 0;
fac[0] = 1;
for (int i = 1; i <= n; ++i)
fac[i] = mul(fac[i - 1], i);
invfac[n] = fpow(fac[n], P - 2);
for (int i = n - 1; i >= 0; --i)
invfac[i] = mul(invfac[i + 1], i + 1);
poly res = Prod(0, n - 2);
//	for (int i = 0; i <= n - 1; ++i)
//		printf("%d ", res[i]);
//	puts("");
cout << mul(res[A + B], binom(A + B, A)) << '\n';
return 0;
}


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Time: ? ms, memory: ? KB
Verdict: ?
Input
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Participant's output
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