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| #include<cmath>
#include<cstdio>
#include<cstring>
#include<iostream>
#include<algorithm>
#include<vector>
using namespace std;
#define sqz main
#define ll long long
#define rep(i, a, b) for (int i = (a); i <= (b); i++)
#define per(i, a, b) for (int i = (a); i >= (b); i--)
#define Rep(i, a, b) for (int i = (a); i < (b); i++)
#define travel(i, u) for (int i = head[u]; ~i; i = edge[i].next)
const ll INF = 1e9, Mo = INF + 7;
const int N = 263000;
const double eps = 1e-6, pi = acos(-1.0);
ll read()
{
ll x = 0; int zf = 1; char ch = getchar();
while (ch != '-' && (ch < '0' || ch > '9')) ch = getchar();
if (ch == '-') zf = -1, ch = getchar();
while (ch >= '0' && ch <= '9') x = x * 10 + ch - '0', ch = getchar();
return x * zf;
}
void write(ll y)
{
if (y < 0) putchar('-'), y = -y;
if (y > 9) write(y / 10);
putchar(y % 10 + '0');
}
char st[N + 5], S[N + 5];
int Ans[N + 5], X[N + 5], Y[N + 5], Rev[N + 5];
int t;
void Manacher(char *S, int len, int *Rad)
{
for (int i = 0, j = 0, k; i < len; i += k)
{
while (S[i - j - 1] == S[i + j + 1]) j++;
Rad[i] = j;
for (k = 1; k <= j && j - k != Rad[i - k]; k++) Rad[i + k] = min(j - k, Rad[i - k]);
j = max(j - k, 0);
}
}
ll pow(ll a, ll b, ll Mo)
{
ll ans = 1;
while (b)
{
if (b & 1) ans = ans * a % Mo;
a = a * a % Mo;
b >>= 1;
}
return ans;
}
struct Complex
{
double real, imagine;
Complex (double real = 0, double imagine = 0) : real(real), imagine(imagine) {};
Complex operator +(const Complex X)
{
return Complex(real + X.real, imagine + X.imagine);
}
Complex operator -(const Complex X)
{
return Complex(real - X.real, imagine - X.imagine);
}
Complex operator *(const Complex X)
{
return Complex(real * X.real - imagine * X.imagine, real * X.imagine + imagine * X.real);
}
}XX[N + 5], YY[N + 5];
void FFT(Complex *T, int n, int op)
{
Rep(i, 0, n) if (i < Rev[i]) swap(T[i], T[Rev[i]]);
for (int Size = 1; Size < n; Size <<= 1)
{
Complex wn = Complex(cos(pi / Size), sin(pi / Size) * op);
for (int L = 0; L < n; L += (Size << 1))
{
Complex w = Complex(1, 0);
Rep(R, L, L + Size)
{
Complex x = T[R], y = w * T[R + Size];
T[R] = x + y, T[R + Size] = x - y;
w = w * wn;
}
}
}
}
void Mul(int *T, int n)
{
int x = 2 * n;
int l = 0; for (t = 1; t <= x; t <<= 1) l++;
Rep(i, 0, t) Rev[i] = (Rev[i >> 1] >> 1) + ((i & 1) << l - 1);
Rep(i, 0, n) XX[i] = YY[i] = Complex(T[i], 0);
Rep(i, n, t) XX[i] = YY[i] = Complex(0, 0);
FFT(XX, t, 1); FFT(YY, t, 1);
Rep(i, 0, t) XX[i] = XX[i] * YY[i];
FFT(XX, t, -1);
rep(i, 0, x) T[i] = (int)(XX[i].real / t + 0.5);
}
int sqz()
{
scanf("%s", st);
int len = strlen(st); st[len] = ')';
S[0] = '(';
rep(i, 0, len) S[2 * i + 1] = '#', S[2 * (i + 1)] = st[i];
len = len * 2 + 3;
Manacher(S, len, Ans);
int ans1 = 0, ans2 = 0;
Rep(i, 0, len) (ans1 += (Ans[i] + 1) / 2) %= Mo;
len = strlen(st) - 1;
Rep(i, 0, len) if (st[i] == 'a') X[i] = 1;
else Y[i] = 1;
Mul(X, len); Mul(Y, len);
rep(i, 0, 2 * len) (ans2 += pow(2, (X[i] + 1) / 2 + (Y[i] + 1) / 2, Mo) - 1) %= Mo;
printf("%d\n", (ans2 - ans1 + Mo) % Mo);
}
|
