HNOI2004 宠物收养所 splay

看清楚题意后居然一A了，这么长的代码一A对我来说还真是少见。

突然弄懂了数组版splay的内存池的原理，还是很简单的。。。

#include<bits/stdc++.h>
#define REP(i,a,b) for(int i=a;i<=b;i++)
#define MS0(a) memset(a,0,sizeof(a))

using namespace std;

typedef long long ll;
const int maxn=1000100;
const int INF=1e9+10;
const int MOD=1000000;

int n;
int op,x;
struct Splay
{
    ll key[maxn];
    int pre[maxn],ch[maxn][2],rt,tot1;
    int s[maxn],tot2;
    void newnode(int &r,int fa,ll k)
    {
        if(tot2) r=s[tot2--];
        else r=++tot1;
        key[r]=k;pre[r]=fa;
        MS0(ch[r]);
    }
    void rot(int x,int kind)
    {
        int y=pre[x];
        ch[y][kind^1]=ch[x][kind];
        pre[ch[x][kind]]=y;
        if(pre[y]) ch[pre[y]][ch[pre[y]][1]==y]=x;
        pre[x]=pre[y];
        ch[x][kind]=y;
        pre[y]=x;
    }
    void splay(int x,int goal)
    {
        while(pre[x]!=goal){
            if(pre[pre[x]]==goal) rot(x,ch[pre[x]][0]==x);
            else{
                int y=pre[x],z=pre[y];
                int kind=ch[y][0]==x,one=0;
                if(ch[y][0]==x&&ch[z][0]==y) one=1;
                if(ch[y][1]==x&&ch[z][1]==y) one=1;
                if(one) rot(y,kind),rot(x,kind);
                else rot(x,kind),rot(x,kind^1);
            }
        }
        if(goal==0) rt=x;
    }
    void Del()
    {
        if(!ch[rt][0]&&!ch[rt][1]) rt=0,tot1=tot2=0;
        else if(!ch[rt][0]) s[++tot2]=rt,rt=ch[rt][1],pre[rt]=0;
        else if(!ch[rt][1]) s[++tot2]=rt,rt=ch[rt][0],pre[rt]=0;
        else{
            int r=ch[rt][0];
            while(ch[r][1]) r=ch[r][1];
            splay(r,rt);
            s[++tot2]=rt;
            ch[r][1]=ch[rt][1];
            pre[ch[r][1]]=r;
            rt=r;
            pre[rt]=0;
        }
    }
    int Find(ll k)
    {
        if(rt==0) return 0;
        int r=rt,f=0;
        while(r){
            if(key[r]==k){
                splay(r,0);
                return 1;
            }
            f=r;
            r=ch[r][k>key[r]];
        }
        splay(f,0);
        return 0;
    }
    void Insert(ll x)
    {
        if(rt==0) newnode(rt,0,x);
        else{
            int r=rt,f=0;
            while(r){
                if(key[r]==x){
                    splay(r,0);
                    return;
                }
                f=r;r=ch[r][x>key[r]];
            }
            newnode(ch[f][x>key[f]],f,x);
            splay(ch[f][x>key[f]],0);
        }
    }
    void init()
    {
        rt=tot1=0;
        tot2=0;
        MS0(pre);MS0(key);MS0(ch);
    }
    ll get_pre(int x)
    {
        if(!ch[x][0]) return -1;
        x=ch[x][0];
        while(ch[x][1]) x=ch[x][1];
        return key[x];
    }
    ll get_next(int x)
    {
        if(!ch[x][1]) return -1;
        x=ch[x][1];
        while(ch[x][0]) x=ch[x][0];
        return key[x];
    }
};Splay A,P;

int main()
{
    freopen("in.txt","r",stdin);
    while(cin>>n){
        A.init();P.init();
        ll ans=0;
        REP(i,1,n){
            scanf("%d%d",&op,&x);
            if(op==0){
                if(P.rt!=0){
                    if(P.Find(x)) P.Del();
                    else{
                        int y=P.key[P.rt],z;
                        if(x<y){
                            z=P.get_pre(P.rt);
                            if(z!=-1&&abs(x-z)<=abs(x-y)) P.Find(z);
                            P.Del();
                        }
                        else{
                            z=P.get_next(P.rt);
                            if(z!=-1&&abs(x-y)>abs(x-z)) P.Find(z);
                            P.Del();
                        }
                        if(z!=-1) ans+=min(abs(x-z),abs(x-y));
                        else ans+=abs(x-y);
                        //cout<<"x="<<x<<" y="<<y<<" z="<<z<<endl;
                        ans%=MOD;
                    }
                }
                else A.Insert(x);
            }
            else{
                if(A.rt!=0){
                    if(A.Find(x)) A.Del();
                    else{
                        ll y=A.key[A.rt],z;
                        if(x<y){
                            z=A.get_pre(A.rt);
                            if(z!=-1&&abs(x-z)<=abs(x-y)) A.Find(z);
                            A.Del();
                        }
                        else{
                            z=A.get_next(A.rt);
                            if(z!=-1&&abs(x-y)>abs(x-z)) A.Find(z);
                            A.Del();
                        }
                        if(z!=-1) ans+=min(abs(x-z),abs(x-y));
                        else ans+=abs(x-y);
                        //cout<<"x="<<x<<" y="<<y<<" z="<<z<<endl;
                        ans%=MOD;
                    }
                }
                else P.Insert(x);
            }
        }
        cout<<ans%MOD<<endl;
    }
    return 0;
}