[ZJOI2008] Tree Tree Statistics Split chain

[ZJOI2008] tree statistics

Face questions

Bare tree section, while maintaining a segment tree sumand maxjust fine.1A celebrate half an hour this question.

Also note that, while supporting tree line "range modification" and "range query" only need to use the lazy tag.

#include <cstdio>
#include <algorithm>
#define MAXN 30003
#define sl (x<<1)
#define sr (x<<1|1)
using namespace std;
int head[MAXN],nxt[MAXN*2],vv[MAXN*2],tot;
inline void add_edge(int u, int v){
    vv[++tot]=v;
    nxt[tot]=head[u];
    head[u]=tot;
}
int fa[MAXN],dep[MAXN],sz[MAXN],mxs[MAXN];
void dfs1(int u, int f){
    dep[u]=dep[f]+1;
    fa[u]=f;
    sz[u]=1;
    int mxsz=-1;
    for(int i=head[u];i;i=nxt[i]){
        int v=vv[i];
        if(v==f) continue;
        dfs1(v, u);
        sz[u]+=sz[v];
        if(mxsz<sz[v]){
            mxsz=sz[v];
            mxs[u]=v;
        }
    }
}
int w[MAXN],wnew[MAXN];
int topf[MAXN],idx[MAXN],cnt;
void dfs2(int u, int top){
    topf[u]=top;
    idx[u]=++cnt;
    wnew[cnt]=w[u];
    if(mxs[u]==0) return;
    dfs2(mxs[u], top);
    for(int i=head[u];i;i=nxt[i]){
        int v=vv[i];
        if(v==fa[u]||v==mxs[u]) continue;
        dfs2(v,v);
    }
}
struct nod{
    int sum,mx;
} tre[MAXN*4];
int n;
void push_up(int x){
    tre[x].sum=tre[sl].sum+tre[sr].sum;
    tre[x].mx=max(tre[sl].mx, tre[sr].mx);
}
void buildt(int x, int l, int r){
    if(l==r){
        tre[x].sum=tre[x].mx=wnew[l];
        return;
    }
    int mid=(l+r)>>1;
    buildt(sl, l, mid);
    buildt(sr, mid+1, r);
    push_up(x);
}
void change(int x, int cx, int l, int r, int val){
    if(l==r){
        tre[x].sum=tre[x].mx=val;
        return;
    }
    int mid=(l+r)>>1;
    if(cx<=mid) change(sl, cx, l, mid, val);
    else change(sr, cx, mid+1, r, val);
    push_up(x);
}
int query_mx(int x, int ql, int qr, int l, int r){
    if(ql<=l&&r<=qr){
        return tre[x].mx;
    }
    int mid=(l+r)>>1;
    int ans=-30000;
    if(ql<=mid) ans=max(query_mx(sl, ql, qr, l, mid), ans);
    if(mid<qr) ans=max(query_mx(sr, ql, qr, mid+1, r), ans);
    return ans;
}
int query_sum(int x, int ql, int qr, int l, int r){
    if(ql<=l&&r<=qr){
        return tre[x].sum;
    }
    int mid=(l+r)>>1;
    int ans=0;
    if(ql<=mid) ans+=query_sum(sl, ql, qr, l, mid);
    if(mid<qr) ans+=query_sum(sr, ql, qr, mid+1, r);
    return ans;
}
int tre_query_mx(int a, int b){
    int ans=-30000;
    while(topf[a]!=topf[b]){
        if(dep[topf[a]]<dep[topf[b]]) swap(a,b);
        ans=max(ans, query_mx(1, idx[topf[a]], idx[a], 1, n));
        a=fa[topf[a]];
    }
    if(dep[a]<dep[b]) swap(a,b);
    ans=max(query_mx(1, idx[b], idx[a], 1, n), ans);
    return ans;
}
int tre_query_sum(int a, int b){
    int ans=0;
    while(topf[a]!=topf[b]){
        if(dep[topf[a]]<dep[topf[b]]) swap(a,b);
        ans+=query_sum(1, idx[topf[a]], idx[a], 1, n);
        a=fa[topf[a]];
    }
    if(dep[a]<dep[b]) swap(a,b);
    ans+=query_sum(1, idx[b], idx[a], 1, n);
    return ans;
}
int main()
{
    scanf("%d", &n);
    for(int i=2;i<=n;++i){
        int a,b;
        scanf("%d %d", &a, &b);
        add_edge(a,b);
        add_edge(b,a);
    }
    for(int i=1;i<=n;++i) scanf("%d", &w[i]);
    dfs1(1, 1);
    dfs2(1, 1);
    buildt(1, 1, n);
    int q;
    scanf("%d", &q);
    while(q--){
        char s[10];
        int a,b;
        scanf("%s%d%d", s, &a, &b);
        if(s[1]=='H') change(1, idx[a], 1, n, b);
        else if(s[1]=='M') printf("%d\n", tre_query_mx(a,b));
        else if(s[1]=='S') printf("%d\n", tre_query_sum(a,b));
        else puts("Erro!");
    }
    return 0;
}