(CCPC 2020 网络选拔赛)HDU 6900 Residual Polynomial(分治 + NTT)
Residual Polynomial
寫出所有的fi(x)f_i(x)fi?(x)出來,fi,jf_{i, j}fi,j?表示fi(x)f_i(x)fi?(x)的第jjj項系數
{f1,0f1,1f1,2…f1,n?1f1,nf2,0f2,1f2,2…f2,n?1f2,nf3,0f3,1f3,2…f3,n?1f3,n??????fn?1,0fn?1,1fn?1,2…fn?1,n?1fn?1,nfn,0fn,1fn,2…fn,n?1fn,n}\left\{ \begin{matrix} f_{1, 0} & f_{1, 1} & f_{1, 2} & \dots & f_{1, n - 1} & f_{1, n}\\ f_{2, 0} & f_{2, 1} & f_{2, 2} & \dots & f_{2, n - 1} & f_{2, n}\\ f_{3, 0} & f_{3, 1} & f_{3, 2} & \dots & f_{3, n - 1} & f_{3, n}\\ \vdots & \vdots & \vdots & \ddots & \vdots & \vdots\\ f_{n - 1, 0} & f_{n - 1, 1} & f_{n - 1, 2} & \dots & f_{n - 1, n - 1} & f_{n - 1, n}\\ f_{n, 0} & f_{n, 1} & f_{n, 2} & \dots & f_{n, n - 1} & f_{n, n}\\ \end{matrix} \right\} ??????????????????f1,0?f2,0?f3,0??fn?1,0?fn,0??f1,1?f2,1?f3,1??fn?1,1?fn,1??f1,2?f2,2?f3,2??fn?1,2?fn,2??………?……?f1,n?1?f2,n?1?f3,n?1??fn?1,n?1?fn,n?1??f1,n?f2,n?f3,n??fn?1,n?fn,n????????????????????
第一行是a0,a1,a2,…,an?1,ana_0, a_1, a_2, \dots, a_{n - 1}, a_{n}a0?,a1?,a2?,…,an?1?,an?。
考慮下一行如何從上一行轉移,分兩種:
一、fi,j×ci+1=fi+1,jf_{i, j} \times c_{i + 1} = f_{i + 1, j}fi,j?×ci+1?=fi+1,j?
二、fi,j×j×bi+1=fi+1,j?1f_{i, j} \times j \times b_{i + 1} = f_{i + 1, j - 1}fi,j?×j×bi+1?=fi+1,j?1?
可以想想成每個點有一條向下的連邊value=cvalue = cvalue=c,同時有一條向左下的連邊value=b×jvalue = b \times jvalue=b×j。
我們從f1,if_{1, i}f1,i?出發,走向fn,jf_{n, j}fn,j?,顯然選擇了i?ji- ji?j個b×jb \times jb×j,所以還有n?1?(i?j)n - 1 - (i - j)n?1?(i?j)個ccc。
先不考慮jjj,只算b,cb, cb,c的貢獻,設選bbb的生成函數為F(x)F(x)F(x),對于某個點有F(x)=c+bxF(x) = c + bxF(x)=c+bx,因為上面的轉移是具有區間性的。
所以F(l,r,x)=F(l,mid,x)?F(mid,r,x)F(l, r, x) = F(l, mid, x) * F(mid, r, x)F(l,r,x)=F(l,mid,x)?F(mid,r,x),也就是在左區間選幾個,右區間選幾個,然后組合一下,這個組合剛好滿足卷積的形式。
這一步就可以遞歸O(nlog?nlog?n)O(n \log n \log n)O(nlognlogn)求解了。
接下來考慮jjj的影響:
fn,k=∑i?k=jF(j)f1,ii!k!f_{n, k} = \sum\limits_{i - k = j} F(j)f_{1, i} \frac{i!}{k!}fn,k?=i?k=j∑?F(j)f1,i?k!i!?
這里可以簡單理解一下,每次只能向左向下移動,k是我們最后在的列,只能從初始列i≥ki \geq ki≥k的列轉移過來。
(k!×fn,k)=∑i?k=jF(j)(f1,i×i!)\left(k! \times f_{n, k}\right) = \sum\limits_{i - k = j} F(j) \left(f_{1, i} \times i!\right)(k!×fn,k?)=i?k=j∑?F(j)(f1,i?×i!)
設H(k)=k!×fn,k,G(i)=f1,i×i!設H(k) = k! \times f_{n, k}, G(i) = f_{1, i} \times i !設H(k)=k!×fn,k?,G(i)=f1,i?×i!,考慮把G翻轉,G(n?i)=G(i)考慮把G翻轉,G(n - i) = G(i)考慮把G翻轉,G(n?i)=G(i),
H(k)=∑i+j=n?kF(j)G(i)H(k) = \sum_{i + j = n - k} F(j) G(i)H(k)=∑i+j=n?k?F(j)G(i),于是再做一次卷積即可求得答案。
#include <bits/stdc++.h>using namespace std;const int mod = 998244353, inv2 = mod + 1 >> 1;namespace Quadratic_residue {struct Complex {int r, i;Complex(int _r = 0, int _i = 0) : r(_r), i(_i) {}};int I2;Complex operator * (const Complex &a, Complex &b) {return Complex((1ll * a.r * b.r % mod + 1ll * a.i * b.i % mod * I2 % mod) % mod, (1ll * a.r * b.i % mod + 1ll * a.i * b.r % mod) % mod);}Complex quick_pow(Complex a, int n) {Complex ans = Complex(1, 0);while (n) {if (n & 1) {ans = ans * a;}a = a * a;n >>= 1;}return ans;}int get_residue(int n) {mt19937 e(233);if (n == 0) {return 0;}if(quick_pow(n, (mod - 1) >> 1).r == mod - 1) {return -1;}uniform_int_distribution<int> r(0, mod - 1);int a = r(e);while(quick_pow((1ll * a * a % mod - n + mod) % mod, (mod - 1) >> 1).r == 1) {a = r(e);}I2 = (1ll * a * a % mod - n + mod) % mod;int x = quick_pow(Complex(a, 1), (mod + 1) >> 1).r, y = mod - x;if(x > y) swap(x, y);return x;} }const int N = 1e6 + 10;int r[N], inv[N], b[N], c[N], d[N], e[N], t[N];int quick_pow(int a, int n) {int ans = 1;while (n) {if (n & 1) {ans = 1ll * a * ans % mod;}a = 1ll * a * a % mod;n >>= 1;}return ans; }void get_r(int lim) {for (int i = 0; i < lim; i++) {r[i] = (i & 1) * (lim >> 1) + (r[i >> 1] >> 1);} }void get_inv(int n) {inv[1] = 1;for (int i = 2; i <= n; i++) {inv[i] = 1ll * (mod - mod / i) * inv[mod % i] % mod;} }void NTT(int *f, int lim, int rev) {for (int i = 0; i < lim; i++) {if (i < r[i]) {swap(f[i], f[r[i]]);}}for (int mid = 1; mid < lim; mid <<= 1) {int wn = quick_pow(3, (mod - 1) / (mid << 1));for (int len = mid << 1, cur = 0; cur < lim; cur += len) {int w = 1;for (int k = 0; k < mid; k++, w = 1ll * w * wn % mod) {int x = f[cur + k], y = 1ll * w * f[cur + mid + k] % mod;f[cur + k] = (x + y) % mod, f[cur + mid + k] = (x - y + mod) % mod;}}}if (rev == -1) {int inv = quick_pow(lim, mod - 2);reverse(f + 1, f + lim);for (int i = 0; i < lim; i++) {f[i] = 1ll * f[i] * inv % mod;}} }void polyinv(int *f, int *g, int n) {if (n == 1) {g[0] = quick_pow(f[0], mod - 2);return ;}polyinv(f, g, n + 1 >> 1);for (int i = 0; i < n; i++) {t[i] = f[i];}int lim = 1;while (lim < 2 * n) {lim <<= 1;}get_r(lim);NTT(t, lim, 1);NTT(g, lim, 1);for (int i = 0; i < lim; i++) {int cur = (2 - 1ll * g[i] * t[i] % mod + mod) % mod;g[i] = 1ll * g[i] * cur % mod;t[i] = 0;}NTT(g, lim, -1);for (int i = n; i < lim; i++) {g[i] = 0;} }void polysqrt(int *f, int *g, int n) {if (n == 1) {g[0] = Quadratic_residue::get_residue(f[0]);return ;}polysqrt(f, g, n + 1 >> 1);polyinv(g, b, n);int lim = 1;while (lim < 2 * n) {lim <<= 1;}get_r(lim);for (int i = 0; i < n; i++) {t[i] = f[i];}NTT(g, lim, 1);NTT(b, lim, 1);NTT(t, lim, 1);for (int i = 0; i < lim; i++) {g[i] = (1ll * inv2 * g[i] % mod + 1ll * inv2 * b[i] % mod * t[i] % mod) % mod;b[i] = t[i] = 0;}NTT(g, lim, -1);for (int i = n; i < lim; i++) {g[i] = 0;} }void derivative(int *a, int *b, int n) {for (int i = 0; i < n; i++) {b[i] = 1ll * a[i + 1] * (i + 1) % mod;} }void integrate(int *a, int n) {for (int i = n - 1; i >= 1; i--) {a[i] = 1ll * a[i - 1] * inv[i] % mod;}a[0] = 0; }void polyln(int *f, int *g, int n) {polyinv(f, b, n);derivative(f, g, n);int lim = 1;while (lim < 2 * n) {lim <<= 1;}get_r(lim);NTT(g, lim, 1);NTT(b, lim, 1);for (int i = 0; i < lim; i++) {g[i] = 1ll * g[i] * b[i] % mod;b[i] = 0;}NTT(g, lim, -1);for (int i = n; i < lim; i++) {g[i] = 0;}integrate(g, n); }void polyexp(int *f, int *g, int n) {if (n == 1) {g[0] = 1;return ;}polyexp(f, g, n + 1 >> 1);int lim = 1;while (lim < 2 * n) {lim <<= 1;}polyln(g, d, n);for (int i = 0; i < n; i++) {t[i] = (f[i] - d[i] + mod) % mod;}t[0] = (t[0] + 1) % mod;get_r(lim);NTT(g, lim, 1);NTT(t, lim, 1);for (int i = 0; i < lim; i++) {g[i] = 1ll * g[i] * t[i] % mod;t[i] = d[i] = 0;}NTT(g, lim, -1);for (int i = n; i < lim; i++) {g[i] = 0;} }/*b存放多項式逆,c存放多項式開根,d存放多項式對數ln,e存放多項式指數exp,t作為中間轉移數組,如果要用到polyln,得提前調用get_inv(n)先預先得到我們想要得到的逆元范圍。 */int B[N], C[N], f[N], fac[N], inv1[N], n;vector<int> F[N];int A1[N], B1[N];void init() {fac[0] = 1;for (int i = 1; i < N; i++) {fac[i] = 1ll * fac[i - 1] * i % mod;}inv1[N - 1] = quick_pow(fac[N - 1], mod - 2);for (int i = N - 2; i >= 0; i--) {inv1[i] = 1ll * inv1[i + 1] * (i + 1) % mod;} }void merge(int rt) {int ls = rt << 1, rs = rt << 1 | 1;int n = F[ls].size(), m = F[rs].size();F[rt].resize(n + m);for (int i = 0; i < n + m; i++) {F[rt][i] = 0;}if (n <= 50 && m <= 50) {for (int i = 0; i < n; i++) {for (int j = 0; j < m; j++) {F[rt][i + j] = (F[rt][i + j] + 1ll * F[ls][i] * F[rs][j] % mod) % mod;}}return ;}for (int i = 0; i < n; i++) {A1[i] = F[ls][i];}for (int i = 0; i < m; i++) {B1[i] = F[rs][i];}int lim = 1;while (lim < n + m) {lim <<= 1;}get_r(lim);NTT(A1, lim, 1);NTT(B1, lim, 1);for (int i = 0; i < lim; i++) {A1[i] = 1ll * A1[i] * B1[i] % mod;}NTT(A1, lim, -1);for (int i = 0; i < n + m; i++) {F[rt][i] = A1[i];}for (int i = 0; i < lim; i++) {A1[i] = B1[i] = 0;} }void divide(int rt, int l, int r) {if (l == r) {F[rt].push_back(C[l]);F[rt].push_back(B[l]);return ;}int mid = l + r >> 1;divide(rt << 1, l, mid), divide(rt << 1 | 1, mid + 1, r);merge(rt);F[rt << 1].clear(), F[rt << 1 | 1].clear(); }int main() {// freopen("in.txt", "r", stdin);// freopen("out.txt", "w", stdout);// ios::sync_with_stdio(false), cin.tie(0), cout.tie(0);int T;init();scanf("%d", &T);while (T--) {scanf("%d", &n);for (int i = 0; i <= n; i++) {scanf("%d", &f[i]);f[i] = 1ll * f[i] * fac[i] % mod;}for (int i = 0; i <= n - 2; i++) {scanf("%d", &B[i]);}for (int i = 0; i <= n - 2; i++) {scanf("%d", &C[i]);}divide(1, 0, n - 2);int lim = 1;while (lim <= 2 * n) {lim <<= 1;}get_r(lim);for (int i = 0; i <= n; i++) {A1[i] = f[n - i];}for (int i = 0; i < F[1].size(); i++) {B1[i] = F[1][i];}F[1].clear();NTT(A1, lim, 1);NTT(B1, lim, 1);for (int i = 0; i < lim; i++) {A1[i] = 1ll * A1[i] * B1[i] % mod;}NTT(A1, lim, -1);for (int i = 0; i <= n; i++) {printf("%lld%c", 1ll * inv1[i] * A1[n - i] % mod, i == n ? '\n' : ' ');}for (int i = 0; i < lim; i++) {A1[i] = B1[i] = 0;}}return 0; }總結
以上是生活随笔為你收集整理的(CCPC 2020 网络选拔赛)HDU 6900 Residual Polynomial(分治 + NTT)的全部內容,希望文章能夠幫你解決所遇到的問題。
- 上一篇: (linux nohup)
- 下一篇: HDU 6755 Fibonacci S