标签:color type namespace efi view turn eof lock family
Fn = c2n-6 * Fn-1 * Fn-2 * Fn-3,求 Fn .
推一下式子,变成 Fn * cn = ( Fn-1 * cn-1 ) * ( Fn-2 * cn-2 ) * ( Fn-3 * cn-3 )
记 Tn = Fn * cn,就有 Tn = Tn-1 * Tn-2 * Tn-3 .
再推一下,Tn = Tn-22 * Tn-32 * Tn-4,
发现数列的指数是可以 ( a , b , c ) ----- > ( b+a , c+a , a ) 递推的,
这个显然是可以矩阵乘法优化的,式子很容易推就不放了。
要注意的是矩阵乘法求出来的是指数,所以中间过程是对 p - 1 取模,
因为 at mod p = at mod (p-1) mod p,p为质数,a 和 p 互质 .
1 #include<bits/stdc++.h> 2 #define rep(i,a,b) for(register int i=a;i<=b;++i) 3 #define rpd(i,a,b) for(register int i=a;i>=b;--i) 4 #define rep1(i,x) for(register int i=head[x];i;i=nxt[i]) 5 typedef long long ll; 6 const int N=10+5; 7 const ll Mod=1000000007LL; 8 using namespace std; 9 inline int read(){ 10 int x=0,f=1;char ch=getchar(); 11 while(!isdigit(ch)){if(ch==‘-‘)f=-1;ch=getchar();} 12 while(isdigit(ch)){x=x*10+ch-‘0‘;ch=getchar();} 13 return x*f; 14 } 15 ll n,f1,f2,f3,c0;ll a[N][N],f[N][N],ans[N][N],a1[N][N],b1[N][N],anss[N][N]; 16 void work(ll a[N][N],ll b[N][N],ll c[N][N],int x,int y){ 17 rep(i,1,x)rep(j,1,3)a1[i][j]=a[i][j]; 18 rep(i,1,y)rep(j,1,3)b1[i][j]=b[i][j]; 19 rep(i,1,x)rep(j,1,y){ 20 ll sum=0; 21 rep(t,1,3)(sum+=(a1[i][t]*b1[t][j])%(Mod-1LL))%=(Mod-1LL); 22 c[i][j]=sum; 23 } 24 } 25 void mul(ll now){ 26 while(now){ 27 if(now&1)work(a,f,f,3,3); 28 work(a,a,a,3,3); 29 now>>=1; 30 } 31 } 32 ll pow(ll x,ll k){ 33 if(k==0)return 1LL; 34 if(k==1)return x; 35 ll t=pow(x,k/2LL);t*=t;t%=Mod; 36 if(k&1)t*=x,t%=Mod; 37 return t; 38 } 39 int main(){ 40 cin>>n>>f1>>f2>>f3>>c0; 41 memset(f,0,sizeof(f)); 42 rep(i,1,3)f[i][i]=1LL; 43 a[1][1]=1LL;a[1][2]=1LL;a[1][3]=1LL; 44 a[2][1]=1LL;a[2][2]=0;a[2][3]=0; 45 a[3][1]=0;a[3][2]=1LL;a[3][3]=0; 46 mul(n-4LL); 47 ans[1][1]=ans[1][2]=ans[1][3]=1LL; 48 memset(anss,0,sizeof(anss)); 49 work(ans,f,anss,1,3); 50 rep(i,1,3)(f3*=c0)%=Mod; 51 rep(i,1,2)(f2*=c0)%=Mod; 52 rep(i,1,1)(f1*=c0)%=Mod; 53 ll now=1LL;(now*=pow(f3,anss[1][1]))%=Mod; 54 (now*=pow(f2,anss[1][2]))%=Mod; 55 (now*=pow(f1,anss[1][3]))%=Mod; 56 ll nows=pow(c0,n);nows=pow(nows,Mod-2LL); 57 (now*=nows)%=Mod; 58 printf("%lld\n",now); 59 //system("pause"); 60 return 0; 61 }
[矩阵乘法] CF 1182 E.Product Oriented Recurrence
标签:color type namespace efi view turn eof lock family
原文地址:https://www.cnblogs.com/maximumhanyu/p/11428440.html