Luogu P3384 【模板】树链剖分

。。。rt。。。安利一发大佬博客https://www.cnblogs.com/ivanovcraft/p/9019090.html

注意：不要把dfn和rw弄混了。。。

#include<cstdio>
#include<iostream>
#define ll long long
#define R register ll
#define ls (tr<<1)
#define rs (tr<<1|1)
const int M=;
using namespace std;
inline ll g() {
    R ret=; register char ch; while(!isdigit(ch=getchar())) ;
    do ret=ret*+(ch^); while(isdigit(ch=getchar())); return ret;
}
int n,m,tr,cnt,num,mod;
int vr[M<<],nxt[M<<],fir[M],dfn[M],pre[M],d[M],sz[M],son[M],top[M],rw[M],w[M];
int tg[M<<],sum[M<<];
inline void add(int u,int v) {vr[++cnt]=v,nxt[cnt]=fir[u],fir[u]=cnt;}
void dfs(int u) { sz[u]=; R mx=;
    for(R i=fir[u];i;i=nxt[i]) { R v=vr[i];
        if(!d[v]) {
            pre[v]=u; d[v]=d[u]+; dfs(v); sz[u]+=sz[v];
            if(sz[v]>mx) son[u]=v,mx=sz[v];
        }
    }
}
void dfs_(int u,int tp) {
    top[u]=tp,dfn[u]=++num,rw[num]=u;
    if(son[u]) dfs_(son[u],tp);
    for(R i=fir[u];i;i=nxt[i]) { R v=vr[i];
        if(v!=pre[u]&&v!=son[u]) dfs_(v,v);
    }
}
inline void build(int tr,int l,int r) {
    if(l==r) {sum[tr]=w[rw[l]]; if(sum[tr]>=mod) sum[tr]%=mod; return ;}
    R md=(l+r)>>; build(ls,l,md),build(rs,md+,r);
    sum[tr]=(sum[ls]+sum[rs])%mod;
}
inline void spread(int tr,int len) {
    if(tg[tr])
        (tg[ls]+=tg[tr])%=mod,(sum[ls]+=(len-(len>>))*tg[tr])%=mod,
        (tg[rs]+=tg[tr])%=mod,(sum[rs]+=(len>>)*tg[tr])%=mod,tg[tr]=;
}
inline int query(int tr,int l,int r,int LL,int RR) { R ret=;
    if(LL<=l&&r<=RR) {return sum[tr];} spread(tr,r-l+); R md=(l+r)>>;
    if(LL<=md) (ret+=query(ls,l,md,LL,RR))%=mod;
    if(RR>md) (ret+=query(rs,md+,r,LL,RR))%=mod; return ret;
}
inline void update(int tr,int l,int r,int LL,int RR,int inc) {
    if(LL<=l&&r<=RR) {(tg[tr]+=inc)%=mod,(sum[tr]+=(r-l+)*inc)%=mod; return ;}
    spread(tr,r-l+); R md=(l+r)>>;
    if(LL<=md) update(ls,l,md,LL,RR,inc);
    if(RR>md) update(rs,md+,r,LL,RR,inc);
    sum[tr]=(sum[ls]+sum[rs])%mod;
}
inline void change(int u,int v,int inc) {
    while(top[u]!=top[v]) {
        if(d[top[u]]<d[top[v]]) swap(u,v);
        update(,,n,dfn[top[u]],dfn[u],inc);
        u=pre[top[u]];
    } if(dfn[u]>dfn[v]) swap(u,v);
    update(,,n,dfn[u],dfn[v],inc);
}
inline int qTree(int u,int v) {
    R ret=;
    while(top[u]!=top[v]) {
        if(d[top[u]]<d[top[v]]) swap(u,v);
        (ret+=query(,,n,dfn[top[u]],dfn[u]))%=mod;
        u=pre[top[u]];
    } if(dfn[u]>dfn[v]) swap(u,v); (ret+=query(,,n,dfn[u],dfn[v]))%=mod;
    return ret;
}
signed main() {
    n=g(),m=g(),tr=g(),mod=g();
    for(R i=;i<=n;++i) w[i]=g();
    for(R i=,u,v;i<n;++i) u=g(),v=g(),add(u,v),add(v,u); cnt=;
    d[tr]=; dfs(tr),dfs_(tr,tr); build(,,n);
    //for(R i=1;i<=n;++i) cout<<sz[i]<<d[i]<<dfn[i]<<pre[i]<<son[i]<<top[i]<<endl;
    for(R i=;i<=m;++i) {
        R k=g(),u=g(),v,inc; //cout<<k<<u<<endl;
        if(k==) v=g(),inc=g(),change(u,v,inc%mod);
        else if(k==) v=g(),printf("%lld\n",qTree(u,v));
        else if(k==) v=g(),update(,,n,dfn[u],dfn[u]+sz[u]-,v%mod);
        else printf("%lld\n",query(,,n,dfn[u],dfn[u]+sz[u]-));
    }
}

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2019.04.19