2019.03.18【洛谷P5245】【模板】多项式快速幂(NTT)(多项式Ln)(多项式Exp)

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传送门


解析:

直接做的话还是可以 m o d    p \mod p 后做快速幂,那样的话就有两个 log \log

实际上由于 a 0 = 1 a_0=1 ,可以考虑两边取对数:

ln B ( x ) = k ln A ( x ) \ln B(x)=k\ln A(x)

取对数,一乘,再exp回去就做完了。


代码:

#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define re register
#define gc get_char
#define cs const

namespace IO{
	inline char get_char(){
		static cs int Rlen=1<<20|1;
		static char buf[Rlen],*p1,*p2;
		return (p1==p2)&&(p2=(p1=buf)+fread(buf,1,Rlen,stdin),p1==p2)?EOF:*p1++;
	}
	
	inline int getint(){
		re char c;
		while(!isdigit(c=gc()));re int num=c^48;
		while(isdigit(c=gc()))num=(num+(num<<2)<<1)+(c^48);
		return num;
	}
}
using namespace IO;

cs int mod=998244353;
inline int add(int a,int b){return a+b>=mod?a+b-mod:a+b;}
inline int dec(int a,int b){return a<b?a-b+mod:a-b;}
inline int mul(int a,int b){return (ll)a*b%mod;}
inline int quickpow(int a,int b,int res=1){
	while(b){
		if(b&1)res=mul(res,a);
		a=mul(a,a);
		b>>=1;
	}
	return res;
}


cs int N=410000;
int inv[N],r[N];
inline void NTT(int *A,int n,int typ){
	for(int re i=0;i<n;++i)if(i<r[i])swap(A[i],A[r[i]]);
	for(int re i=1;i<n;i<<=1){
		int wn=quickpow(typ==-1?(mod+1)/3:3,(mod-1)/i/2);
		for(int re j=0;j<n;j+=i<<1)
		for(int re k=0,x,y,w=1;k<i;++k,w=mul(w,wn)){
			x=A[j+k],y=mul(w,A[j+k+i]);
			A[j+k]=add(x,y);
			A[j+k+i]=dec(x,y);
		}
	}
	if(typ==-1)for(int re i=0;i<n;++i)A[i]=mul(A[i],inv[n]);
}

inline void deriv(int *A,int *B,int len){
	for(int re i=1;i<len;++i)B[i-1]=mul(i,A[i]);B[len-1]=0;
}

inline void integ(int *A,int *B,int len){
	for(int re i=1;i<len;++i)B[i]=mul(inv[i],A[i-1]);B[0]=0;
}

inline void Inv(int deg ,int *a,int *b){
	static int c[N];
	if(deg==1)return (void)(b[0]=quickpow(a[0],mod-2));
	Inv((deg+1)>>1,a,b);
	memset(c,0,sizeof c);
	int re len=1;
	while(len<(deg<<1))len<<=1;
	for(int re i=0;i<len;++i)r[i]=(r[i>>1]>>1)|((i&1)*(len>>1));
	memcpy(c,a,sizeof(int)*deg);
	memset(c+deg,0,sizeof(int)*(len-deg));
	NTT(c,len,1),NTT(b,len,1);
	for(int re i=0;i<=len;++i)b[i]=mul(b[i],dec(2,mul(b[i],c[i])));
	NTT(b,len,-1);
	memset(b+deg,0,sizeof(int)*(len-deg));
}

inline void Ln(int deg,int *f,int *g){
	static int a[N],b[N];
	memset(a,0,sizeof(a));memset(b,0,sizeof(b));
	deriv(f,a,deg);
	Inv(deg,f,b);
	int re len=1;
	while(len<(deg<<1))len<<=1;
	for(int re i=0;i<len;++i)r[i]=(r[i>>1]>>1)|((i&1)*(len>>1));
	NTT(a,len,1),NTT(b,len,1);
	for(int re i=0;i<len;++i)a[i]=mul(a[i],b[i]);
	NTT(a,len,-1);
	integ(a,g,len);
	memset(g+deg,0,sizeof(int)*(len-deg));
}

inline void Exp(int deg,int *a,int *b){
	if(deg==1){b[0]=1;return ;}
	static int F[N];
	Exp((deg+1)>>1,a,b);
	memset(F,0,sizeof F);
	Ln(deg,b,F);
	F[0]=dec(a[0]+1,F[0]);
	for(int re i=1;i<deg;++i)F[i]=dec(a[i],F[i]);
	int re len=1;
	while(len<=deg)len<<=1;
	for(int re i=0;i<len;++i)r[i]=(r[i>>1]>>1)|((i&1)*(len>>1));
	NTT(F,len,1),NTT(b,len,1);
	for(int re i=0;i<len;++i)b[i]=mul(b[i],F[i]);
	NTT(b,len,-1);
	memset(b+deg,0,sizeof(int)*(len-deg));
}

inline void init_inv(){
	inv[0]=inv[1]=1;
	for(int re i=2;i<N;++i)inv[i]=mul(inv[mod%i],mod-mod/i);
}

int n,k;
inline int getmod(){
	re char c;
	while(!isdigit(c=gc()));re int num=c^48;
	while(isdigit(c=gc()))num=add(mul(num,10),c^48);
	return num;
}

int a[N],b[N],c[N]; 
signed main(){
	init_inv();
	n=getint();
	k=getmod();
	for(int re i=0;i<n;++i)a[i]=getint();
	int re len=1;
	while(len<=n)len<<=1;
	Ln(n,a,c);
	for(int re i=0;i<n;++i)a[i]=mul(c[i],k);
	memset(a+n,0,sizeof(int)*(len-n));
	Exp(len,a,b);
	for(int re i=0;i<n;++i)cout<<b[i]<<" ";
	return 0;
}

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转载自blog.csdn.net/zxyoi_dreamer/article/details/88647635