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  • 任意模数fft

    1.正常拆系数fft,8次dft

    //#pragma GCC optimize(2)
    //#pragma GCC optimize(3)
    //#pragma GCC optimize(4)
    //#pragma GCC optimize("unroll-loops")
    //#pragma comment(linker, "/stack:200000000")
    //#pragma GCC optimize("Ofast,no-stack-protector")
    //#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
    #include<bits/stdc++.h>
    //#include <bits/extc++.h>
    #define fi first
    #define se second
    #define db double
    #define mp make_pair
    #define pb push_back
    #define mt make_tuple
    //#define pi acos(-1.0)
    #define ll long long
    #define vi vector<int>
    #define mod 1000000007
    #define ld long double
    //#define C 0.5772156649
    #define ls l,m,rt<<1
    #define rs m+1,r,rt<<1|1
    #define sqr(x) ((x)*(x))
    #define pll pair<ll,ll>
    #define pil pair<int,ll>
    #define pli pair<ll,int>
    #define pii pair<int,int>
    #define ull unsigned long long
    #define bpc __builtin_popcount
    #define base 1000000000000000000ll
    #define fin freopen("a.txt","r",stdin)
    #define fout freopen("a.txt","w",stdout)
    #define fio ios::sync_with_stdio(false);cin.tie(0)
    #define mr mt19937 rng(chrono::steady_clock::now().time_since_epoch().count())
    inline ll gcd(ll a,ll b){return b?gcd(b,a%b):a;}
    inline void sub(ll &a,ll b){a-=b;if(a<0)a+=mod;}
    inline void add(ll &a,ll b){a+=b;if(a>=mod)a-=mod;}
    template<typename T>inline T const& MAX(T const &a,T const &b){return a>b?a:b;}
    template<typename T>inline T const& MIN(T const &a,T const &b){return a<b?a:b;}
    inline ll qp(ll a,ll b){ll ans=1;while(b){if(b&1)ans=ans*a%mod;a=a*a%mod,b>>=1;}return ans;}
    inline ll qp(ll a,ll b,ll c){ll ans=1;while(b){if(b&1)ans=ans*a%c;a=a*a%c,b>>=1;}return ans;}
    
    using namespace std;
    //using namespace __gnu_pbds;
    
    const ld pi=acos(-1);
    const ull ba=233;
    const db eps=1e-5;
    const ll INF=0x3f3f3f3f3f3f3f3f;
    const int N=400000+10,maxn=2000000+10,inf=0x3f3f3f3f;
    
    struct cd{
        ld x,y;
        cd(ld _x=0.0,ld _y=0.0):x(_x),y(_y){}
        cd operator +(const cd &b)const{
            return cd(x+b.x,y+b.y);
        }
        cd operator -(const cd &b)const{
            return cd(x-b.x,y-b.y);
        }
        cd operator *(const cd &b)const{
            return cd(x*b.x - y*b.y,x*b.y + y*b.x);
        }
        cd operator /(const db &b)const{
            return cd(x/b,y/b);
        }
    }a[N],b[N],c[N],d[N];
    int rev[N],A[N],B[N],C[N];
    void getrev(int bit)
    {
        for(int i=0;i<(1<<bit);i++)
            rev[i]=(rev[i>>1]>>1) | ((i&1)<<(bit-1));
    }
    void fft(cd *a,int n,int dft)
    {
        for(int i=0;i<n;i++)if(i<rev[i])swap(a[i],a[rev[i]]);
        for(int step=1;step<n;step<<=1)
        {
            cd wn(cos(dft*pi/step),sin(dft*pi/step));
            for(int j=0;j<n;j+=step<<1)
            {
                cd wnk(1,0);
                for(int k=j;k<j+step;k++)
                {
                    cd x=a[k];
                    cd y=wnk*a[k+step];
                    a[k]=x+y;a[k+step]=x-y;
                    wnk=wnk*wn;
                }
            }
        }
        if(dft==-1)for(int i=0;i<n;i++)a[i]=a[i]/n;
    }
    void mtt(int n,int m,int p) {
        int sz=0;
        while((1<<sz)<=n+m)sz++;getrev(sz);
        int len=1<<sz;
        for(int i=0;i<len;i++)
        {
            int t1=A[i]%p,t2=B[i]%p;
            a[i]=cd(t1>>15,0),b[i]=cd(t1&0x7fff,0);
            c[i]=cd(t2>>15,0),d[i]=cd(t2&0x7fff,0);
        }
        fft(a,len,1);fft(b,len,1);fft(c,len,1);fft(d,len,1);
        for(int i=0;i<len;i++)
        {
            cd aa=a[i],bb=b[i],cc=c[i],dd=d[i];
            a[i]=aa*cc;b[i]=bb*cc;c[i]=aa*dd;d[i]=bb*dd;
        }
        fft(a,len,-1);fft(b,len,-1);fft(c,len,-1);fft(d,len,-1);
        for(int i=0;i<len;i++)
        {
            ll aa=(ll)(a[i].x+0.5),bb=(ll)(b[i].x+0.5);
            ll cc=(ll)(c[i].x+0.5),dd=(ll)(d[i].x+0.5);
            aa=(aa%p+p)%p;bb=(bb%p+p)%p;cc=(cc%p+p)%p;dd=(dd%p+p)%p;
            C[i]=((((aa<<15)%p)<<15)%p+(bb<<15)%p+(cc<<15)%p+dd)%p;
        }
    }
    int main()
    {
        int n,m,p;scanf("%d%d%d",&n,&m,&p);
        for(int i=0;i<=n;i++)scanf("%d",&A[i]);
        for(int i=0;i<=m;i++)scanf("%d",&B[i]);
        mtt(n,m,p);
        for(int i=0;i<=n+m;i++)printf("%d ",C[i]);
        return 0;
    }
    /********************
    
    ********************/
    

    2.黑科技优化拆系数fft,4次dft

    //#pragma GCC optimize(2)
    //#pragma GCC optimize(3)
    //#pragma GCC optimize(4)
    //#pragma GCC optimize("unroll-loops")
    //#pragma comment(linker, "/stack:200000000")
    //#pragma GCC optimize("Ofast,no-stack-protector")
    //#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
    #include<bits/stdc++.h>
    //#include <bits/extc++.h>
    #define fi first
    #define se second
    #define db double
    #define mp make_pair
    #define pb push_back
    #define mt make_tuple
    //#define pi acos(-1.0)
    #define ll long long
    #define vi vector<int>
    #define mod 1000000007
    #define ld long double
    //#define C 0.5772156649
    #define ls l,m,rt<<1
    #define rs m+1,r,rt<<1|1
    #define sqr(x) ((x)*(x))
    #define pll pair<ll,ll>
    #define pil pair<int,ll>
    #define pli pair<ll,int>
    #define pii pair<int,int>
    #define ull unsigned long long
    #define bpc __builtin_popcount
    #define base 1000000000000000000ll
    #define fin freopen("a.txt","r",stdin)
    #define fout freopen("a.txt","w",stdout)
    #define fio ios::sync_with_stdio(false);cin.tie(0)
    #define mr mt19937 rng(chrono::steady_clock::now().time_since_epoch().count())
    inline ll gcd(ll a,ll b){return b?gcd(b,a%b):a;}
    inline void sub(ll &a,ll b){a-=b;if(a<0)a+=mod;}
    inline void add(ll &a,ll b){a+=b;if(a>=mod)a-=mod;}
    template<typename T>inline T const& MAX(T const &a,T const &b){return a>b?a:b;}
    template<typename T>inline T const& MIN(T const &a,T const &b){return a<b?a:b;}
    inline ll qp(ll a,ll b){ll ans=1;while(b){if(b&1)ans=ans*a%mod;a=a*a%mod,b>>=1;}return ans;}
    inline ll qp(ll a,ll b,ll c){ll ans=1;while(b){if(b&1)ans=ans*a%c;a=a*a%c,b>>=1;}return ans;}
    
    using namespace std;
    //using namespace __gnu_pbds;
    
    const ull ba=233;
    const db eps=1e-5;
    const ld pi=acos(-1);
    const ll INF=0x3f3f3f3f3f3f3f3f;
    const int N=270000+10,maxn=2000000+10,inf=0x3f3f3f3f;
    
    struct cd{
        ld x,y;
        cd(ld _x=0.0,ld _y=0.0):x(_x),y(_y){}
        cd operator +(const cd &b)const{
            return cd(x+b.x,y+b.y);
        }
        cd operator -(const cd &b)const{
            return cd(x-b.x,y-b.y);
        }
        cd operator *(const cd &b)const{
            return cd(x*b.x - y*b.y,x*b.y + y*b.x);
        }
        cd operator /(const db &b)const{
            return cd(x/b,y/b);
        }
    }a[N],b[N],dfta[N],dftb[N],dftc[N],dftd[N];
    cd conj(cd a){return cd(a.x,-a.y);}
    int rev[N],A[N],B[N],C[N];
    void getrev(int bit)
    {
        for(int i=0;i<(1<<bit);i++)
            rev[i]=(rev[i>>1]>>1) | ((i&1)<<(bit-1));
    }
    void fft(cd *a,int n,int dft)
    {
        for(int i=0;i<n;i++)if(i<rev[i])swap(a[i],a[rev[i]]);
        for(int step=1;step<n;step<<=1)
        {
            cd wn(cos(dft*pi/step),sin(dft*pi/step));
            for(int j=0;j<n;j+=step<<1)
            {
                cd wnk(1,0);
                for(int k=j;k<j+step;k++)
                {
                    cd x=a[k];
                    cd y=wnk*a[k+step];
                    a[k]=x+y;a[k+step]=x-y;
                    wnk=wnk*wn;
                }
            }
        }
        if(dft==-1)for(int i=0;i<n;i++)a[i]=a[i]/n;
    }
    void mtt(int n,int m,int p) {
        int sz=0;
        while((1<<sz)<=n+m)sz++;getrev(sz);
        int len=1<<sz;
        for(int i=0;i<len;i++)
        {
            int x=(i>n?0:A[i]%p),y=(i>m?0:B[i]%p);
            a[i]=cd(x&0x7fff,x>>15);
            b[i]=cd(y&0x7fff,y>>15);
        }
        fft(a,len,1);fft(b,len,1);
        for(int i=0;i<len;i++)
        {
            int j=(len-i)&(len-1);
            cd aa,bb,cc,dd;
            aa = (a[i] + conj(a[j])) * cd(0.5, 0);
            bb = (a[i] - conj(a[j])) * cd(0, -0.5);
            cc = (b[i] + conj(b[j])) * cd(0.5, 0);
            dd = (b[i] - conj(b[j])) * cd(0, -0.5);
            dfta[j] = aa * cc;dftb[j] = aa * dd;
            dftc[j] = bb * cc;dftd[j] = bb * dd;
        }
        for(int i=0;i<len;i++)
        {
            a[i] = dfta[i] + dftb[i] * cd(0, 1);
            b[i] = dftc[i] + dftd[i] * cd(0, 1);
        }
        fft(a,len,1);fft(b,len,1);
        for(int i=0;i<len;i++)
        {
            int da = (ll)(a[i].x / len + 0.5) % p;
            int bb = (ll)(a[i].y / len + 0.5) % p;
            int dc = (ll)(b[i].x / len + 0.5) % p;
            int dd = (ll)(b[i].y / len + 0.5) % p;
            C[i] = (da + ((ll)(bb + dc) << 15) + ((ll)dd << 30)) % p;
            C[i] = (C[i]+p)%p;
        }
    }
    int main()
    {
        int n,m,p;scanf("%d%d%d",&n,&m,&p);
        for(int i=0;i<=n;i++)scanf("%d",&A[i]);
        for(int i=0;i<=m;i++)scanf("%d",&B[i]);
        mtt(n,m,p);
        for(int i=0;i<=n+m;i++)printf("%d ",C[i]);
        return 0;
    }
    /********************
    
    ********************/
    
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  • 原文地址:https://www.cnblogs.com/acjiumeng/p/11109702.html
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