Hdu 4695 线性递推模版(m^2logn)

本文介绍了一种利用线性递推和矩阵快速幂技术解决特定类型数列求值问题的方法。通过构建高效的算法,可以在较短时间内计算出数列的第n项值,适用于动态规划转移方程优化等场景。

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#include <bits/stdc++.h>
#pragma comment(linker, "/STACK:102400000,102400000")
using namespace std;
typedef long long ll;
#define LL long long
const int mod=1e9+7;
const int MOD=1e9+7;
const int MAXN=205;
ll n;
int u, d;
int a[100], b[100];
ll dp[205];
ll A[205];
ll C[205];

// given first m a[i] and coef (0 based)
// calc a[n] % MOD in O(m*m*log(n))
// a[n] = sum(c[m - i] * a[n - i]) i = 1....m
// a[m] = sum(c[i] * a[i]), i = 0.....m-1

LL linear_recurrence(LL n, int m, LL a[], LL c[], int p){ //n->a[i], m -> c[i]
    LL v[MAXN] = {1 % MOD}, u[MAXN << 1], msk = !!n;
    for(LL i = n; i > 1; i >>= 1) msk <<= 1;
    for(LL x = 0; msk; msk >>= 1, x <<= 1){
        fill_n(u, m << 1, 0);
        int b = !!(n & msk); x |= b;
        if(x < m) u[x] = 1 % p;
        else{
            for(int i = 0; i < m; i++){
                for(int j = 0, t = i + b; j < m; ++j, ++t)
                    u[t] = (u[t] + v[i] * v[j]) % MOD;
            }
            for(int i = (m << 1) - 1; i >= m; --i){
                for(int j = 0, t = i - m; j < m; ++j, ++t){
                    u[t] = (u[t] + c[j] * u[i]) % MOD;
                }
            }
        }
        copy(u, u+m, v);
    }
    LL ans = 0;
    for(int i = 0; i < m; i++){
        ans = (ans + v[i] * a[i]) % MOD;
    }
    return ans;
}

bool vis[205];
int main()
{
    while(~scanf("%lld", &n)){
        int ma=0;
        memset(dp, 0, sizeof(dp));
        memset(A, 0, sizeof(A));
        memset(C, 0, sizeof(C));
        memset(vis, false, sizeof(vis));
        scanf("%d", &u);
        for(int i=1;i<=u;i++){scanf("%d", &a[i]);}
        scanf("%d", &d);
        for(int i=1;i<=d;i++){scanf("%d", &b[i]);ma=max(b[i], ma);vis[b[i]]=true;}
        dp[0]=1;
        for(int i=1;i<=ma;i++){
            for(int j=1;j<=u;j++){
                if(i<a[j])continue;
                dp[i]=(dp[i-a[j]]+dp[i])%mod;
            }
        }
        vis[0]=true;
        for(int i=0;i<=ma;i++)if(!vis[i])dp[i]=0;
        for(int i=0;i<ma;i++){C[i]=dp[ma-i];}
        A[0]=1;
        for(int i=1;i<ma;i++){
            for(int j=1;j<=i;j++){
                A[i]=(A[i]+A[i-j]*dp[j])%mod;
            }
        }
        ll ans=linear_recurrence(n, ma, A, C, mod);
        printf("%lld\n", ans);
    }
}

UPD:杜教BM模板无敌!此贴终结

#include <cstdio>
#include <cstring>
#include <cmath>
#include <algorithm>
#include <vector>
#include <string>
#include <map>
#include <set>
#include <cassert>
#include<bits/stdc++.h>
using namespace std;
#define rep(i,a,n) for (int i=a;i<n;i++)
#define per(i,a,n) for (int i=n-1;i>=a;i--)
#define pb push_back
#define mp make_pair
#define all(x) (x).begin(),(x).end()
#define fi first
#define se second
#define SZ(x) ((int)(x).size())
typedef vector<int> VI;
typedef long long ll;
typedef pair<int,int> PII;
const ll mod=1000000007;
ll powmod(ll a,ll b) {ll res=1;a%=mod; assert(b>=0); for(;b;b>>=1){if(b&1)res=res*a%mod;a=a*a%mod;}return res;}
// head

int _;
ll n;
namespace linear_seq {
    const int N=10010;
    ll res[N],base[N],_c[N],_md[N];

    vector<int> Md;
    void mul(ll *a,ll *b,int k) {
        rep(i,0,k+k) _c[i]=0;
        rep(i,0,k) if (a[i]) rep(j,0,k) _c[i+j]=(_c[i+j]+a[i]*b[j])%mod;
        for (int i=k+k-1;i>=k;i--) if (_c[i])
            rep(j,0,SZ(Md)) _c[i-k+Md[j]]=(_c[i-k+Md[j]]-_c[i]*_md[Md[j]])%mod;
        rep(i,0,k) a[i]=_c[i];
    }
    int solve(ll n,VI a,VI b) { // a 系数 b 初值 b[n+1]=a[0]*b[n]+...
        //        printf("%d\n",SZ(b));
        ll ans=0,pnt=0;
        int k=SZ(a);
        assert(SZ(a)==SZ(b));
        rep(i,0,k) _md[k-1-i]=-a[i];_md[k]=1;
        Md.clear();
        rep(i,0,k) if (_md[i]!=0) Md.push_back(i);
        rep(i,0,k) res[i]=base[i]=0;
        res[0]=1;
        while ((1ll<<pnt)<=n) pnt++;
        for (int p=pnt;p>=0;p--) {
            mul(res,res,k);
            if ((n>>p)&1) {
                for (int i=k-1;i>=0;i--) res[i+1]=res[i];res[0]=0;
                rep(j,0,SZ(Md)) res[Md[j]]=(res[Md[j]]-res[k]*_md[Md[j]])%mod;
            }
        }
        rep(i,0,k) ans=(ans+res[i]*b[i])%mod;
        if (ans<0) ans+=mod;
        return ans;
    }
    VI BM(VI s) {
        VI C(1,1),B(1,1);
        int L=0,m=1,b=1;
        rep(n,0,SZ(s)) {
            ll d=0;
            rep(i,0,L+1) d=(d+(ll)C[i]*s[n-i])%mod;
            if (d==0) ++m;
            else if (2*L<=n) {
                VI T=C;
                ll c=mod-d*powmod(b,mod-2)%mod;
                while (SZ(C)<SZ(B)+m) C.pb(0);
                rep(i,0,SZ(B)) C[i+m]=(C[i+m]+c*B[i])%mod;
                L=n+1-L; B=T; b=d; m=1;
            } else {
                ll c=mod-d*powmod(b,mod-2)%mod;
                while (SZ(C)<SZ(B)+m) C.pb(0);
                rep(i,0,SZ(B)) C[i+m]=(C[i+m]+c*B[i])%mod;
                ++m;
            }
        }
        return C;
    }
    int gao(VI a,ll n) {
        VI c=BM(a);
        c.erase(c.begin());
        rep(i,0,SZ(c)) c[i]=(mod-c[i])%mod;
        return solve(n,c,VI(a.begin(),a.begin()+SZ(c)));
    }
};

int a[55],an;
int b[55],bn;
int dp[403];
int dp2[403];

int main() {
    while (~scanf("%lld",&n)) {
        memset(dp,0,sizeof(dp));
        memset(dp2,0,sizeof(dp2));
        scanf("%d",&an);
        for(int i=1;i<=an;i++){
            scanf("%d",&a[i]);
        }
        dp[0]=1;
        for(int i=1;i<=400;i++){
            for(int j=1;j<=an;j++){
                if(i>=a[j]){
                    dp[i]=(dp[i]+dp[i-a[j]])%mod;
                }
            }
        }
        scanf("%d",&bn);
        for(int i=1;i<=bn;i++){
            scanf("%d",&b[i]);
        }
        dp2[0]=1;
        for(int i=1;i<=400;i++){
            for(int j=1;j<=bn;j++){
                if(i>=b[j]){
                    dp2[i]=(dp2[i]+1ll*dp2[i-b[j]]*dp[b[j]])%mod;
                }
            }
        }
        vector<int>v;
        for(int i=0;i<=400;i++)v.push_back(dp2[i]);
        //VI{1,2,4,7,13,24}
        printf("%d\n",linear_seq::gao(v,n));
    }
}
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