BZOJ 1036 && Luogu P2590 [ZJOI2008]树的统计 树链剖分

链剖裸题。。。你值得一做~

用线段树多维护一个mx，少写一个tag

#include<cstdio>
#include<iostream>
#define ll long long
#define R register ll
#define ls (tr<<1)
#define rs (tr<<1|1)
using namespace std;
const int N=;
inline ll g() {
    R ret=,fix=; register char ch; while(!isdigit(ch=getchar())) fix=ch=='-'?-:fix;
    do ret=ret*+(ch^); while(isdigit(ch=getchar())); return ret*fix;
}
int n,m,cnt,num,mod;
int vr[N<<],nxt[N<<],fir[N],dfn[N],pre[N],son[N],d[N],sz[N],top[N],rw[N],w[N];
ll sum[N<<],mx[N<<];
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]) continue; 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) {mx[tr]=sum[tr]=w[rw[l]]; return ;}
    R md=(l+r)>>; build(ls,l,md),build(rs,md+,r);
    sum[tr]=sum[ls]+sum[rs],mx[tr]=max(mx[ls],mx[rs]);
}
inline ll queryS(int tr,int l,int r,int LL,int RR) {
    if(LL<=l&&r<=RR) return sum[tr]; R md=(l+r)>>,ret=;
    if(LL<=md) ret+=queryS(ls,l,md,LL,RR); if(RR>md) ret+=queryS(rs,md+,r,LL,RR);
    return ret;
}
inline ll queryM(int tr,int l,int r,int LL,int RR) {
    if(LL<=l&&r<=RR) return mx[tr]; R md=(l+r)>>,ret=-;
    if(LL<=md) ret=max(queryM(ls,l,md,LL,RR),ret); if(RR>md) ret=max(queryM(rs,md+,r,LL,RR),ret);
    return ret;
}
inline void update(int tr,int l,int r,int pos,ll inc) {
    if(l==r) {mx[tr]=sum[tr]=inc; return ;}
    R md=(l+r)>>; if(pos<=md) update(ls,l,md,pos,inc); else update(rs,md+,r,pos,inc);
    sum[tr]=sum[ls]+sum[rs],mx[tr]=max(mx[ls],mx[rs]);
}
inline ll queryTS(int u,int v) { R ret=;
    while(top[u]!=top[v]) {
        if(d[top[u]]<d[top[v]]) swap(u,v);
        ret+=queryS(,,n,dfn[top[u]],dfn[u]);
        u=pre[top[u]];
    } if(dfn[u]>dfn[v]) swap(u,v); ret+=queryS(,,n,dfn[u],dfn[v]);
    return ret;
}
inline ll queryTM(int u,int v) { R ret=-;
    while(top[u]!=top[v]) {
        if(d[top[u]]<d[top[v]]) swap(u,v);
        ret=max(queryM(,,n,dfn[top[u]],dfn[u]),ret);
        u=pre[top[u]];
    } if(dfn[u]>dfn[v]) swap(u,v); ret=max(queryM(,,n,dfn[u],dfn[v]),ret);
    return ret;
}
inline void print(int tr,int l,int r) {
    if(l==r) {printf("%lld %lld ",sum[tr],mx[tr]); return ;} R md=(l+r)>>;
    print(ls,l,md),print(rs,md+,r);
}
signed main() {
    n=g(); for(R i=,u,v;i<n;++i) u=g(),v=g(),add(u,v),add(v,u);
    for(R i=;i<=n;++i) w[i]=g();
    d[]=top[]=pre[]=; dfs(),dfs_(,); build(,,n); m=g();
    for(R i=;i<=m;++i) { register char ch;
        while(!isalpha(ch=getchar())); ch=getchar(); R u=g(),v=g();
        if(ch=='H') update(,,n,dfn[u],v);
        else if(ch=='M') printf("%lld\n",queryTM(u,v));
        else printf("%lld\n",queryTS(u,v));
    }
}

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想想就有些后怕，自己调了一个半小时，结果发现update没有写dfn[u],而写的u。。。

2019.04.19