题目链接：传送门

Description

给出两个长度为n的数组A,B。求一个子序列，使得子序列中A数组单调不降，B数组单调不升

Solution

本质就是个三维偏序 可以用CDQ分治+树状数组过掉， 但是由于我对Splay情有独钟想练一下Splay，就写的树状数组套Splay 开始写完之后调好久以为是处理权值相同的情况的时候有问题，于是一顿魔改（即读入数据之后的那十几行代码）， 把原数组乱搞成了一个元素互不相同的数组， 后来发现是Splay里面 写错了， 稍微改了下A了之后就懒得把魔改部分改回去了

Code

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#include <bits/stdc++.h>
#define lowbit(x) x & (-x)

using namespace std;

const int Maxn = 5e4 + 10;

int N;
int A[Maxn], B[Maxn], len1, len2;
int Next[Maxn];
int Dp[Maxn], Root[Maxn];

struct node
{
    int val, id;
}X[Maxn], Y[Maxn];
int tmp1[Maxn], tmp2[Maxn];

inline int cmp1 (node a, node b)
{
    if (a.val == b.val) return a.id > b.id;
    return a.val < b.val;
}

inline int cmp2 (node a, node b)
{
    return a.id < b.id;
}

inline int cmp3 (node a, node b)
{
    if (a.val == b.val) return a.id < b.id;
    return a.val < b.val;
}


struct tree
{
    int maxv, maxid, id, val, ch[2], dp, fa;
};

namespace Splay
{
    tree Tree[Maxn * 16];
    int cnt;

    inline int judge_dir (int x)
    {
        return Tree[Tree[x].fa].ch[1] == x;
    }

    inline void chkmax (tree &x, int DP, int ID)
    {
        if (DP > x.maxv) x.maxv = DP, x.maxid = ID;
        else if (DP == x.maxv && ID < x.maxid) x.maxid = ID;
    }

    inline void update (int x)
    {
        Tree[x].maxv = Tree[x].dp;
        Tree[x].maxid = Tree[x].id;
        if (Tree[x].ch[0]) chkmax (Tree[x], Tree[Tree[x].ch[0]].maxv, Tree[Tree[x].ch[0]].maxid);
        if (Tree[x].ch[1]) chkmax (Tree[x], Tree[Tree[x].ch[1]].maxv, Tree[Tree[x].ch[1]].maxid);
    }

    inline void connect (int x, int f, int dir)
    {
        Tree[x].fa = f;
        Tree[f].ch[dir] = x;
    }

    inline void rotate (int x)
    {
        int f = Tree[x].fa; 
        int dirx = judge_dir(x);
        int anc = Tree[f].fa;
        int dirf = judge_dir(f);
        connect(Tree[x].ch[dirx ^ 1], f, dirx);
        connect(f, x, (dirx ^ 1));
        connect(x, anc, dirf);
        update(f), update(x);
    }

    inline void splay (int x, int y, int &root)
    {
        while (Tree[x].fa != y)
        {
            int f = Tree[x].fa;
            int dirx = judge_dir(x), dirf = judge_dir(f);
            if (Tree[f].fa == y) rotate(x);
            else if (dirx == dirf) rotate(f), rotate(x);
            else rotate(x), rotate(x);
        }
        if (!y) root = x;
    }

    inline void Newnode (int val, int DP, int ID, int f)
    {
        Tree[++cnt].val = val;
        Tree[cnt].maxv = Tree[cnt].dp = DP;
        Tree[cnt].maxid = Tree[cnt].id = ID;
        Tree[cnt].fa = f;
    }

    inline void insert (int &root, int val, int DP, int ID)
    {
        if (!root)
        {
            Newnode(val, DP, ID, 0);
            splay (cnt, 0, root);
            return ;
        }
        int now = root;
        while (1)
        {
            if (Tree[now].val == val)
            {
                /*
                tree tmp;
                tmp.maxv = Tree[now].dp;
                tmp.maxid = Tree[now].id;
                chkmax (tmp, DP, ID);
                Tree[now].dp = tmp.maxv;
                Tree[now].id = tmp.maxid;
                splay (now, 0, root);
                */
                /*
                int tmp = Tree[now].ch[1];
                while (Tree[tmp].ch[0]) tmp = Tree[tmp].ch[0];
                Newnode(val, DP, ID, tmp);
                Tree[tmp].ch[0] = cnt;
                splay (cnt, 0, root);
                */
                return ;
            }
            int dir = (val > Tree[now].val);
            if (!Tree[now].ch[dir])
            {
                Newnode(val, DP, ID, now);
                Tree[now].ch[dir] = cnt;
                splay (cnt, 0, root);
                return ;
            }
            now = Tree[now].ch[dir];
        }
    }

    inline void query (int root, int val, tree &save)
    {
        int now = root;
        while (1)
        {
            //cout<<root<<" "<<val<<" "<<now<<" "<<Tree[now].val<<endl;
            if (!now) return ;
            if (Tree[now].val < val)
            {
                now = Tree[now].ch[1];
                continue;
            }
            chkmax (save, Tree[now].dp, Tree[now].id);
            if (Tree[now].ch[1]) chkmax (save, Tree[Tree[now].ch[1]].maxv, Tree[Tree[now].ch[1]].maxid);
            now = Tree[now].ch[0];
        }
    }

}

namespace BIT
{
    inline void add (int x, int y, int DP, int ID)
    {
        while (x <= N)
        {
            Splay :: insert (Root[x], y, DP, ID);
            x += lowbit(x);
        }
    }

    inline void query (int x, int y, int &DP, int &ID)
    {
        tree newnode;
        newnode.maxv = DP;
        newnode.maxid = ID;
        while (x)
        {
            Splay :: query (Root[x], y, newnode);
            x -= lowbit(x);
        }
        DP = newnode.maxv;
        ID = newnode.maxid;
    }
}

inline void Init ()
{
    memset(Dp, 0, sizeof Dp);
    memset(Root, 0, sizeof Root);
    memset(Splay :: Tree, 0, sizeof Splay :: Tree);
    Splay :: cnt = 0;
}

int main()
{
#ifdef hk_cnyali
    freopen("A.in", "r", stdin);
    freopen("A.out", "w", stdout);
#endif
    while (~scanf("%d", &N))
    {
        Init();
        for (int i = 1; i <= N; ++i) scanf("%d", &A[i]), X[i].val = A[i], X[i].id = i;
        for (int i = 1; i <= N; ++i) scanf("%d", &B[i]), Y[i].val = B[i], Y[i].id = i;
        sort(X + 1, X + N + 1, cmp1);
        sort(Y + 1, Y + N + 1, cmp3);
        for (int i = 2; i <= N; ++i)
            if (X[i].val <= X[i - 1].val)
                X[i].val = X[i - 1].val + 1;
        for (int i = 2; i <= N; ++i)
            if (Y[i].val <= Y[i - 1].val)
                Y[i].val = Y[i - 1].val + 1;
        sort(X + 1, X + N + 1, cmp2);
        sort(Y + 1, Y + N + 1, cmp2);
        for (int i = 1; i <= N; ++i) A[i] = X[i].val;
        for (int i = 1; i <= N; ++i) B[i] = Y[i].val;
        sort(X + 1, X + N + 1, cmp1);
        sort(Y + 1, Y + N + 1, cmp3);
        for (int i = 1; i <= N; ++i) tmp1[i] = X[i].val;
        for (int i = 1; i <= N; ++i) tmp2[i] = Y[i].val;
        for (int i = 1; i <= N; ++i) A[i] = lower_bound(tmp1 + 1, tmp1 + N + 1, A[i]) - tmp1;
        for (int i = 1; i <= N; ++i) B[i] = lower_bound(tmp2 + 1, tmp2 + N + 1, B[i]) - tmp2;
        //for (int i = 1; i <= N; ++i) cout<<A[i]<<" ";
        //cout<<endl;
        //for (int i = 1; i <= N; ++i) cout<<B[i]<<" ";
        //cout<<endl;
        int Ans = 0, now = INT_MAX;
        for (int i = N; i >= 1; --i)
        {
            int ID = INT_MAX, DP = 0;
            BIT :: query (A[i], B[i], DP, ID);
            //cout<<A[i]<<" "<<B[i]<<endl;
            //cout<<DP<<" "<<ID<<endl;
            Dp[i] = DP + 1;
            Next[i] = ID;
            BIT :: add (A[i], B[i], Dp[i], i);
            if (Dp[i] >= Ans)
            {
                now = i;
                Ans = Dp[i];
            }
        }
        //for (int i = 1; i <= N; ++i) cout<<Dp[i]<<" ";cout<<endl;
        //for (int i = 1; i <= N; ++i) cout<<Next[i]<<" ";cout<<endl;
        cout<<Ans<<endl;
        while (now != INT_MAX)
        {
            cout<<now;
            now = Next[now];
            if (now != INT_MAX) cout<<" ";
        }
        cout<<endl;
    }
    return 0;
}