【LOJ】#2269. 「SDOI2017」切树游戏

题解

把所有的数组一开始就FWT好然后再IFWT回去可以减小常数
从13s跑到0.7s……

可以参照immortalCO的论文，感受一下毒瘤的动态动态DP

就是用数据结构维护线性递推的矩阵的乘积

由于所有轻儿子\(F(z) + z^{0}\)的乘积做除法太麻烦，我们用一个线段树维护每个点所有的轻儿子即可

代码

#include <bits/stdc++.h>
#define enter putchar('\n')
#define space putchar(' ')
#define fi first
#define se second
#define MAXN 30005
//#define ivorysi
#define pii pair<int,int>
#define pb push_back
using namespace std;
typedef long long int64;
template<class T>
void read(T &res) {
    res = 0;char c = getchar();T f = 1;
    while(c < '0' || c > '9') {
    	if(c == '-') f = -1;
    	c = getchar();
    }
    while(c >= '0' && c <= '9') {
    	res = res * 10 + c - '0';
    	c = getchar();
    }
    res *= f;
}

template<class T>
void out(T x) {
    if(x < 0) {putchar('-');x = -x;}
    if(x >= 10) out(x / 10);
    putchar('0' + x % 10);
}
const int MOD = 10007,Inv2 = 5004;
int mul(int a,int b) {
    return a * b % MOD;
}
int inc(int a,int b) {
    return a + b >= MOD ? a + b - MOD : a + b;
}

struct Enode {
    int to,next;
}E[MAXN * 2];
int N,M,head[MAXN],sumE,val[MAXN],pos[MAXN];
int son[MAXN],siz[MAXN],fa[MAXN],dep[MAXN],top[MAXN];
int rt[MAXN],dfn[MAXN],L[MAXN],id[MAXN],Lcnt,idx;
void add(int u,int v) {
    E[++sumE].to = v;
    E[sumE].next = head[u];
    head[u] = sumE;
}
struct Poly {
    int p[128];
    Poly() {memset(p,0,sizeof(p));}
    friend void FWT(Poly &f) {
        for(int i = 1 ; i < M ; i <<= 1) {
            for(int j = 0 ; j < M ; j += (i << 1)) {
                for(int k = 0 ; k < i ; ++k) {
                    int a0 = f.p[j + k],a1 = f.p[j + i + k];
                    f.p[j + k] = inc(a0,a1);
                    f.p[j + i + k] = inc(a0,MOD - a1);
                }
            }
        }
    }
    friend void IFWT(Poly &f) {
        for(int i = 1 ; i < M ; i <<= 1) {
            for(int j = 0 ; j < M ; j += (i << 1) ) {
                for(int k = 0 ; k < i ; ++k) {
                    int a0 = f.p[j + k],a1 = f.p[j + i + k];
                    f.p[j + k] = mul(inc(a0,a1),Inv2);
                    f.p[j + i + k] = mul(inc(a0,MOD - a1),Inv2);
                }
            }
        }
    }
    friend Poly operator * (Poly a,Poly b) {
        Poly c;
        for(int i = 0 ; i < M ; ++i) c.p[i] = mul(a.p[i],b.p[i]);
        return c;
    }
    friend Poly operator + (const Poly &a,const Poly &b) {
        Poly c;
        for(int i = 0 ; i < M ; ++i) c.p[i] = inc(a.p[i],b.p[i]);
        return c;
    }
    friend Poly operator - (const Poly &a,const Poly &b) {
        Poly c;
        for(int i = 0 ; i < M ; ++i) c.p[i] = inc(a.p[i],MOD - b.p[i]);
        return c;
    }
}F[MAXN],H[MAXN],one,LH[MAXN],LF[MAXN];
struct Matrix {
    Poly a,b,c,d;
    friend Matrix operator * (const Matrix &s,const Matrix &t) {
        Matrix r;
        r.a = s.a * t.a;
        r.b = s.b + s.a * t.b;
        r.c = s.c * t.a + t.c;
        r.d = s.c * t.b + s.d + t.d;
        return r;
    }
};
struct node {
    int lc,rc,L,R;
    Matrix m;
}tr[MAXN * 5];
int Ncnt;
vector<Poly> Tr[MAXN];
vector<int> Lson;
void update(int u) {
    tr[u].m = tr[tr[u].rc].m * tr[tr[u].lc].m;
}
void build(int &u,int l,int r){
    u = ++Ncnt;
    tr[u].L = l;tr[u].R = r;

    if(l == r) {
        int k = L[r];
        Poly t;t.p[val[k]] = 1;FWT(t);
        tr[u].m.a = tr[u].m.b = tr[u].m.c = LF[k] * t;
        tr[u].m.d = LH[k] + tr[u].m.a;
        return ;
    }
    int mid = (l + r) >> 1;
    build(tr[u].lc,l,mid);
    build(tr[u].rc,mid + 1,r);
    update(u);
}

void buildLt(int id,int u,int l,int r) {
    if(l == r) {
        int k = Lson[l - 1];
        Tr[id][u] = F[k] + one;
        pos[k] = u;
        return;
    }
    int mid = (l + r) >> 1;
    buildLt(id,u << 1,l,mid);
    buildLt(id,u << 1 | 1,mid + 1,r);
    Tr[id][u] = Tr[id][u << 1] * Tr[id][u << 1 | 1];
}
void CalcAgain(int u,int pos,int k) {
    if(tr[u].L == tr[u].R) {
        Poly t;t.p[val[k]] = 1;FWT(t);
        tr[u].m.a = tr[u].m.b = tr[u].m.c = LF[k] * t;
        tr[u].m.d = tr[u].m.a + LH[k];
        return ;
    }
    int mid = (tr[u].L + tr[u].R) >> 1;
    if(pos <= mid) CalcAgain(tr[u].lc,pos,k);
    else CalcAgain(tr[u].rc,pos,k);
    update(u);
}
void Change(int u) {
    while(u) {
        CalcAgain(rt[id[u]],dfn[u],u);
        u = top[u];
        if(fa[u]) {
            F[u] = tr[rt[id[u]]].m.c;
            LH[fa[u]] = LH[fa[u]] - H[u] + tr[rt[id[u]]].m.d;
            H[u] = tr[rt[id[u]]].m.d;
            int t = pos[u];Tr[fa[u]][t] = F[u] + one;t >>= 1;
            while(t) {
                Tr[fa[u]][t] = Tr[fa[u]][t << 1] * Tr[fa[u]][t << 1 | 1];
                t >>= 1;
            }
            LF[fa[u]] = Tr[fa[u]][1];
        }
        u = fa[u];
    }
}

void dfs1(int u) {
    siz[u] = 1;dep[u] = dep[fa[u]] + 1;
    F[u].p[val[u]] = 1;FWT(F[u]);
    for(int i = head[u] ; i ; i = E[i].next) {
        int v = E[i].to;
        if(v != fa[u]) {
            fa[v] = u;
            dfs1(v);
            F[u] = F[u] * (F[v] + one);
            H[u] = H[u] + H[v];
            siz[u] += siz[v];
            if(siz[v] > siz[son[u]]) son[u] = v;
        }
    }
    H[u] = H[u] + F[u];
}

void dfs2(int u) {
    LF[u] = one;
    Lson.clear();
    for(int i = head[u] ; i ; i = E[i].next) {
        int v = E[i].to;
        if(v != fa[u] && v != son[u]) {
            Lson.pb(v);
            LF[u] = LF[u] * (F[v] + one);
            LH[u] = LH[u] + H[v];
        }
    }
    if(Lson.size()) {
        Tr[u].resize(Lson.size() * 4 + 5);
        buildLt(u,1,1,Lson.size());
    }
    if(!top[u]) {top[u] = u;++Lcnt;idx = 0;}
    L[++idx] = u;id[u] = Lcnt;dfn[u] = idx;
    if(son[u]) {
        top[son[u]] = top[u];
        dfs2(son[u]);
    }
    else {
        build(rt[Lcnt],1,idx);
        return;
    }
    for(int i = head[u] ; i ; i = E[i].next) {
        int v = E[i].to;
        if(v != fa[u] && v != son[u]) {
            dfs2(v);
        }
    }
}

void Init() {
    read(N);read(M);
    for(int i = 1 ; i <= N ; ++i) read(val[i]);
    int u,v;
    for(int i = 1 ; i < N ; ++i) {
        read(u);read(v);add(u,v);add(v,u);
    }
    one.p[0] = 1;
    FWT(one);
    dfs1(1);dfs2(1);
}

void Solve() {
    int Q;char op[25];int x,y;
    read(Q);
    for(int i = 1 ; i <= Q ; ++i) {
        scanf("%s",op + 1);
        read(x);
        if(op[1] == 'Q') {
            Poly t = tr[rt[id[1]]].m.d;IFWT(t);
            out(t.p[x]);enter;
        }
        else {
            read(y);
            val[x] = y;Change(x);
        }
    }
}
int main() {
#ifdef ivorysi
    freopen("f1.in","r",stdin);
#endif
    Init();
    Solve();
    return 0;
}