HDU 3966 树链剖分学习

这道题不难，看出是树链剖分就很简单，其实奇异也很明显就是一个树链剖分，不过这次不是把树链扔到线段树上，是把节点扔到线段树上。这个时候注意一下w[1] = 1就行了，其他就是线段树的一个区间覆盖的问题了。

#include <iostream>
#include <cstdio>
#include <cstring>
#include <cmath>
#include <algorithm>
#include <map>
#define LL long long
#define FOR(i,x,y)  for(int i = x;i < y;i ++)
#define IFOR(i,x,y) for(int i = x;i > y;i --)
#define lrt rt<<1
#define rrt rt<<1|1
#define lson rt<<1,l,mid
#define rson rt<<1|1,mid+1,r
#define MAXN 55000

using namespace std;

int n,m,p;

struct Edge{
    int u,v;
    int nt;
}edge[MAXN<<1];

int edge_cnt,head[MAXN];

void add_edge(int u,int v){
    edge[edge_cnt].u = u;
    edge[edge_cnt].v = v;
    edge[edge_cnt].nt = head[u];
    head[u] = edge_cnt++;
}

int fa[MAXN],top[MAXN],sz[MAXN],son[MAXN],dep[MAXN],w[MAXN],val[MAXN],totw;

void dfs1(int u,int father,int depth){
    fa[u] = father; sz[u] = 1; dep[u] = depth;
    int idd = -1,maxx = -1;
    for(int i = head[u];i != -1;i = edge[i].nt){
        int v = edge[i].v;
        if(v == father) continue;
        dfs1(v,u,depth+1);
        sz[u] += sz[v];
        if(sz[v] > maxx){
            maxx = sz[v];
            idd = v;
        }
    }
    son[u] = idd;
}

void dfs2(int u,int father){
    if(son[u] == -1)    return;
    top[son[u]] = top[u];
    w[son[u]] = ++totw;
    dfs2(son[u],u);
    for(int i = head[u];i != -1;i = edge[i].nt){
        int v = edge[i].v;
        if(v == father) continue;
        if(v == son[u]) continue;
        top[v] = v;
        w[v] = ++totw;
        dfs2(v,u);
    }
}

struct Tree{
    int l,r;
    int lazy;
}tree[MAXN<<2];

void PushDown(int rt){
    if(tree[rt].lazy){
        tree[lrt].lazy += tree[rt].lazy;
        tree[rrt].lazy += tree[rt].lazy;
        tree[rt].lazy = 0;
    }
}

void Build(int rt,int l,int r){
    tree[rt].l = l; tree[rt].r = r; tree[rt].lazy = 0;
    if(l == r)  return;
    int mid = (l+r)>>1;
    Build(lson);
    Build(rson);
}

void Modify(int rt,int l,int r,int value){
    if(tree[rt].l == l && tree[rt].r == r){
        tree[rt].lazy += value;
        return;
    }
    PushDown(rt);
    int mid = (tree[rt].l + tree[rt].r)>>1;
    if(r <= mid) Modify(lrt,l,r,value);
    else if(l > mid) Modify(rrt,l,r,value);
    else{
        Modify(lson,value);
        Modify(rson,value);
    }
}

int Query(int rt,int x){
    if(tree[rt].l == tree[rt].r){
        return tree[rt].lazy;
    }
    PushDown(rt);
    int mid = (tree[rt].l + tree[rt].r)>>1;
    if(x <= mid)    return Query(lrt,x);
    else return Query(rrt,x);
}

void C_Modify(int l,int r,int value){
    while(top[l] != top[r]){
        if(dep[top[l]] >= dep[top[r]]){
            Modify(1,w[top[l]],w[l],value);
            l = fa[top[l]];
        }
        else{
            Modify(1,w[top[r]],w[r],value);
            r = fa[top[r]];
        }
    }
    if(l == r){
        Modify(1,w[l],w[r],value);
    }
    else if(dep[l] >= dep[r]){
        Modify(1,w[r],w[l],value);
    }
    else Modify(1,w[l],w[r],value);
}

int main()
{
    //freopen("test.in","r",stdin);
    while(~scanf("%d%d%d",&n,&m,&p)){
        FOR(i,1,n+1)    scanf("%d",&val[i]);
        edge_cnt = 0;
        memset(head,-1,sizeof(head));
        FOR(i,0,m){
            int u,v;
            scanf("%d%d",&u,&v);
            add_edge(u,v);
            add_edge(v,u);
        }
        dfs1(1,-1,1);
        totw = 0;
        top[1] = 1;
        w[1] = ++totw;
        dfs2(1,-1);
        Build(1,1,totw);
        FOR(i,0,p){
            char op[10];
            scanf("%s",op);
            if(op[0] == 'I'){
                int l,r,value;
                scanf("%d%d%d",&l,&r,&value);
                C_Modify(l,r,value);
            }
            else if(op[0] == 'D'){
                int l,r,value;
                scanf("%d%d%d",&l,&r,&value);
                C_Modify(l,r,-value);
            }
            else{
                int x;
                scanf("%d",&x);
                printf("%d\n",val[x]+Query(1,w[x]));
            }
        }
    }
    return 0;
}

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