Blog of RuSun

\begin {array}{c} \mathfrak {One Problem Is Difficult} \\\\ \mathfrak {Because You Don't Know} \\\\ \mathfrak {Why It Is Diffucult} \end {array}

CF914G Sum the Fibonacci

LuoGu: CF914G Sum the Fibonacci

CF: G. Sum the Fibonacci

稍微拆一下贡献:
$$
\begin {aligned}
ans &= \sum _ {valid(a, b, c, d, e)}f(s _ a | s _ b) f(s _ c) f (s _ d \oplus s _ e) \\
&= \sum _ {i} \sum _ {x \& y \& z = 2 ^ i}f _ x g _ x f _ y g _ y f _ z g _ z
\end {aligned}
$$
其中,$x = s _ a | s _ b$ ,$g _ x$ 为 $a, b$ 合法的情况数量,$y = s _ b$ ,$z = s _ d \oplus e$ ,$g$ 同理。

发现 $g _ x$ 可以子集卷积,$g _ y$ 显然,$g _ z$ 可以异或卷积,最后三个与卷积即可。

查看代码
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#include <cstdio>
using namespace std;
typedef long long LL;
template <class Type>
void read(Type &x)
{
char c;
bool flag = false;
while ((c = getchar()) < '0' || c > '9')
c == '-' && (flag = true);
x = c - '0';
while ((c = getchar()) >= '0' && c <= '9')
x = (x << 3) + (x << 1) + c - '0';
flag && (x = ~x + 1);
}
template <class Type>
void write(Type x)
{
x < 0 && (putchar('-'), x = ~x + 1);
x > 9 && (write(x / 10), 0);
putchar(x % 10 + '0');
}
const int N = 17, M = 1 << N, mod = 1e9 + 7, inv2 = 5e8 + 4;
int n, fib[M], cnt[M], s[M], A[M], B[M], C[M];
namespace SolveAB
{
int f[N + 1][M], g[N + 1][M];
void fwt (int *x, int op)
{
for (int mid = 1; mid < M; mid <<= 1)
for (int i = 0; i < M; i += mid << 1)
for (int j = 0; j < mid; j++)
(x[i | j | mid] += x[i | j] * op) %= mod;
}
void main ()
{
for (int i = 0; i < M; i++)
f[cnt[i]][i] = s[i];
for (int i = 0; i <= N; i++)
fwt(f[i], 1);
for (int i = 0; i <= N; i++)
for (int j = 0; i + j <= N; j++)
for (int k = 0; k < M; k++)
(g[i + j][k] += (LL)f[i][k] * f[j][k] % mod) %= mod;
for (int i = 0; i <= N; i++)
fwt(g[i], -1);
for (int i = 0; i < M; i++)
A[i] = g[cnt[i]][i];
}
}
namespace SolveC
{
void main ()
{
for (int i = 0; i < M; i++)
B[i] = s[i];
}
}
namespace SolveDE
{
void fwt (int *x, int op)
{
for (int mid = 1; mid < M; mid <<= 1)
for (int i = 0; i < M; i += mid << 1)
for (int j = 0; j < mid; j++)
{
int p = x[i | j], q = x[i | j | mid];
x[i | j] = (LL)(p + q) * op % mod, x[i | j | mid] = (LL)(p - q) * op % mod;
}
}
void main ()
{
for (int i = 0; i < M; i++)
C[i] = s[i];
fwt(C, 1);
for (int i = 0; i < M; i++)
C[i] = (LL)C[i] * C[i] % mod;
fwt(C, inv2);
}
}
namespace Merge
{
void fwt (int *x, int op)
{
for (int mid = 1; mid < M; mid <<= 1)
for (int i = 0; i < M; i += mid << 1)
for (int j = 0; j < mid; j++)
(x[i | j] += x[i | j | mid] * op) %= mod;
}
void main ()
{
fwt(A, 1), fwt(B, 1), fwt(C, 1);
for (int i = 0; i < M; i++)
A[i] = (LL)A[i] * B[i] % mod * C[i] % mod;
fwt(A, -1);
int res = 0;
for (int i = 1; i < M; i <<= 1)
(res += A[i]) %= mod;
write((res + mod) % mod);
}
}
int main ()
{
fib[1] = 1, cnt[1] = 1;
for (int i = 2; i < M; i++)
{
cnt[i] = cnt[i >> 1] + (i & 1);
fib[i] = (fib[i - 2] + fib[i - 1]) % mod;
}
read(n);
for (int a; n; n--)
read(a), s[a]++;
SolveAB::main(), SolveC::main(), SolveDE::main();
for (int i = 0; i < M; i++)
A[i] = (LL)A[i] * fib[i] % mod, B[i] = (LL)B[i] * fib[i] % mod, C[i] = (LL)C[i] * fib[i] % mod;
Merge::main();
return 0;
}