hdu3966 树链剖分+成段更新

 给你n个点，m条边，p次操作。n个点相连后是一棵树。每次操作可以是x 到 y 增加 z，或者减z，或者问当前点的值是多少。

可以将树分成链，每个点在线段树上都有自己的点，然后线段树成段更新一下。

#pragma comment(linker, "/STACK:1024000000,1024000000")
#include<queue>
#include<stack>
#include<cmath>
#include<cstdio>
#include<cstring>
#include<iostream>
#include<algorithm>
#define INF 99999999
#define ll __int64
#define lson l,m,rt<<1
#define rson m+1,r,rt<<1|1
using namespace std;
const int MAXN = 50010;
struct node
{
    int to;
    int v;
    int next;
}edge[MAXN*3];
int pre[MAXN],ind,top[MAXN],fa[MAXN],son[MAXN],w[MAXN],deq[MAXN],siz[MAXN],fn;
int tree[MAXN<<2],mark[MAXN<<2];
int n,m,val[MAXN];
void add(int x,int y)
{
    edge[ind].to = y;
    edge[ind].next = pre[x];
    pre[x] = ind++;
}
void dfs1(int rt,int pa,int d)
{
    deq[rt] = d;
    son[rt] = 0;
    fa[rt] = pa;
    siz[rt] = 1;
    int i;
    for(i=pre[rt]; i!=-1; i=edge[i].next){
        int t = edge[i].to;
        if(t != fa[rt]){
            dfs1(t,rt,d+1);
            siz[rt] += siz[t];
            if(siz[son[rt]] < siz[t]){
                son[rt] = t;
            }
        }
    }
}
void dfs2(int rt,int tp)
{
    w[rt] = ++fn;
    top[rt] = tp;
    if(son[rt] != 0)
        dfs2(son[rt], tp);
    for(int i=pre[rt]; i!=-1; i=edge[i].next){
        int t = edge[i].to;
        if(t != son[rt] && t != fa[rt]){
            dfs2(t,t);
        }
    }
}
void build(int l,int r,int rt)
{
    tree[rt] = 0;
    mark[rt] = 0;
    if(l == r)
        return ;
    int m = (l+r)/2;
    build(lson);
    build(rson);
}
void pushdown(int rt)
{
    if(mark[rt] != 0){
        mark[rt<<1|1] += mark[rt];
        mark[rt<<1] += mark[rt];
        tree[rt<<1|1] += mark[rt];
        tree[rt<<1] += mark[rt];
        mark[rt] = 0;
    }
}
void Insert(int p,int v,int l,int r,int rt)
{
    if(l == r){
        tree[rt] = v;
        return ;
    }
    int m = (l+r)/2;
    if(m >= p){
        Insert(p,v,lson);
    }
    else Insert(p,v,rson);
}
void updata(int L,int R,int v,int l,int r,int rt)
{
    if(L<=l && r<=R){
        mark[rt] += v;
        tree[rt] += v;
        return ;
    }
    pushdown(rt);

    int m = (l+r)/2;
    if(m >= L){
        updata(L,R,v,lson);
    }
    if(m < R){
        updata(L,R,v,rson);
    }
}
int query(int p,int l,int r,int rt)
{
    if(l == r){
        return tree[rt];
    }
    pushdown(rt);
    int m = (l+r)/2;
    if(m >= p){
        return query(p,lson);
    }
    else {
        return query(p,rson);
    }
}
void updata_all(int x,int y,int z)
{
    while(top[x] != top[y])
    {
        if(deq[top[x]] < deq[top[y]]){
            swap(x,y);
        }
        updata(w[top[x]],w[x],z,1,fn,1);

        x = fa[top[x]];
    }
    if(deq[x] < deq[y]){
        swap(x,y);
    }
    updata(w[y],w[x],z,1,fn,1);
}
int main()
{
    int i,j,p;
    while(~scanf("%d%d%d",&n,&m,&p))
    {
        for(i=1; i<=n; i++){
            scanf("%d",&val[i]);
        }
        ind = 1;
        memset(pre,-1,sizeof(pre));
        for(i=1; i<=m; i++){
            int x,y;
            scanf("%d%d",&x,&y);
            add(x,y);
            add(y,x);
        }
        dfs1(1,1,1);
        fn = 0;
        dfs2(1,1);


        build(1,n,1);
        for(i=1; i<=n; i++){
            Insert(w[i],val[i],1,fn,1);
        }
        char s[10];
        while(p--)
        {
            scanf("%s",s);
            if(s[0] == 'I'){
                int x,y,z;
                scanf("%d%d%d",&x,&y,&z);
                updata_all(x,y,z);
            }
            else if(s[0] == 'D'){
                int x,y,z;
                scanf("%d%d%d",&x,&y,&z);
                updata_all(x,y,-z);
            }
            else {
                int x;
                scanf("%d",&x);
                printf("%d
",query(w[x],1,fn,1));
            }
        }
    }
}