HDU 2475 Box 树型转线型 + 伸展树

树型转线型。第一次听说这个概念. . . , 可是曾经已经接触过了，如LCA的预处理部分和树链剖分等。可是没想到还能这么用，三者虽说有不同可是大体思想还是非常相近的，学习了。

推荐博客http://blog.csdn.net/lyhypacm/article/details/6734748

转成线型之后。就变成了伸展树的模板题。

另外要注意，伸展树的特点是平均时间复杂度接近log(n)。所以一定要记得每次操作之后都要伸展。再次学习了。

#include <algorithm>
#include <iostream>
#include <cstring>
#include <cstdlib>
#include <cstdio>
#include <queue>
#include <cmath>
#include <stack>
#include <map>#pragma comment(linker, "/STACK:1024000000");
#define EPS (1e-8)
#define LL long long
#define ULL unsigned long long
#define _LL __int64
#define _INF 0x3f3f3f3f
#define Mod 9999991
#define lowbit(x) (x&(-x))using namespace std;const int MAXN = 50010;struct N
{
    //info
    int son[2],pre,ls,rs,s;    //data
    int id;
} st[MAXN*2];int Top;void Updata(int root)
{
    st[root].ls = (st[root].son[0] == -1 ?0 : st[st[root].son[0]].s);
    st[root].rs = (st[root].son[1] == -1 ? 0 : st[st[root].son[1]].s);
    st[root].s = st[root].ls + st[root].rs + 1;
}void Push_Down(int root)
{
    ;
}void Rotate(int root,int dir)
{
    st[st[root].pre].son[dir] = st[root].son[1^dir];
    st[root].son[1^dir] = st[root].pre;    if(st[st[st[root].pre].pre].son[0] == st[root].pre)
        st[st[st[root].pre].pre].son[0] = root;
    else
        st[st[st[root].pre].pre].son[1] = root;
    int temp = st[root].pre;
    st[root].pre = st[st[root].pre].pre;
    st[temp].pre = root;    if(st[temp].son[dir] != -1)
        st[st[temp].son[dir]].pre = temp;
    Updata(temp);
    Updata(root);
}int Splay(int root,int goal)
{
    while(st[root].pre != goal)
    {
        Rotate(root,(st[st[root].pre].son[0] == root ?0 : 1));
    }    return root;
}int Search_Site(int root,int site)
{
    Push_Down(root);    int temp;    if(st[root].ls + 1 == site)
        temp = root;
    else if(st[root].ls + 1 < site)
        temp = Search_Site(st[root].son[1],site-st[root].ls-1);
    else
        temp = Search_Site(st[root].son[0],site);    Updata(root);
    return temp;
}struct E
{
    int v,next;
} edge[MAXN];int head[MAXN];int degree[MAXN];int Top_E;void Link(int u,int v)
{
    edge[Top_E].v = v;
    edge[Top_E].next = head[u];
    head[u] = Top_E++;
}int vis[MAXN*2];int Top_S;int L[MAXN],R[MAXN];void dfs(int root)
{
    vis[Top_S++] = root;    for(int p = head[root]; p != -1; p = edge[p].next)
    {
        dfs(edge[p].v);
    }    vis[Top_S++] = -root;
}void NewNode(int root,int id,int pre)
{
    st[root].son[0] = -1,st[root].son[1] = -1;
    st[root].pre = pre;    st[root].id = id;
}void Init(int &root,int l,int r,int pre)
{
    if(l > r)
        return ;    int mid = (l+r)>>1;    root = Top++;    NewNode(root,vis[mid],pre);    if(vis[mid] > 0)
        L[vis[mid]] = root;
    else
        R[-vis[mid]] = root;
    Init(st[root].son[0],l,mid-1,root);
    Init(st[root].son[1],mid+1,r,root);    Updata(root);
}int Query(int v)
{
    Splay(L[v],0);
    return st[Search_Site(L[v],1)].id;
}void Move(int u,int v)
{
    if(u == v)
        return ;
    int site = R[v];    Splay(R[u],0);
    Splay(L[u],0);    while(site)
    {
        if(st[site].pre == R[u] && st[R[u]].son[0] == site)
            return ;
        site = st[site].pre;
    }    if(st[L[u]].son[0] != -1)
    {
        int lt = st[L[u]].son[0];
        int rt = st[R[u]].son[1];        st[L[u]].son[0] = -1;
        st[R[u]].son[1] = -1;        Updata(R[u]);
        Updata(L[u]);        st[lt].pre = 0;        int root = Splay(Search_Site(lt,st[lt].s),0);
        st[root].son[1] = rt;
        st[rt].pre = root;
        Updata(root);
    }    if(v)
    {
        Splay(L[v],0);
        Splay(Search_Site(L[v],st[L[v]].ls+2),L[v]);
        st[st[L[v]].son[1]].son[0] = L[u];
        st[L[u]].pre = st[L[v]].son[1];
        Updata(st[L[v]].son[1]);
        Updata(L[v]);
    }
}int main()
{
    int n,m;    int i,j,u,v;    int root;    bool blank = false;    while(scanf("%d",&n) != EOF)
    {
        if(blank)
            printf("\n");
        else
            blank = true;
        Top_E = 0;
        memset(head,-1,sizeof(int)*(n+2));
        memset(degree,0,sizeof(int)*(n+2));        for(i = 1; i <= n; ++i)
        {
            scanf("%d",&u);
            if(u)
            {
                Link(u,i);
                degree[i]++;
            }
        }        st[0].son[0] = -1,st[1].son[1] = -1;        Top = 1;        for(i = 1; i <= n; ++i)
        {
            if(degree[i] == 0)
            {                Top_S = 1;
                dfs(i);                root = -1;
                Init(root,1,Top_S-1,0);
            }
        }        scanf("%d",&m);
        L[0] = R[0] = 0;
        char s[10];
        while(m--)
        {
            scanf("%s",s);
            if(s[0] == 'Q')
            {
                scanf("%d",&u);
                printf("%d\n",Query(u));            }
            else
            {
                scanf("%d %d",&u,&v);
                Move(u,v);
            }
        }
    }
    return 0;
}