洛谷 - P3391 【模板】文艺平衡树（Splay） - 无旋Treap

https://www.luogu.org/problem/P3391

使用无旋Treap维护序列，注意的是按顺序插入的序列，所以Insert实际上简化成直接root和Merge合并，但是假如要在序列中插入某个数，则要SplitRank到正确的位置。

注意SplitRank的写法以及Pushdown的东西。

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
#define ls(p) ch[p][0]
#define rs(p) ch[p][1]

const int MAXN = 200000 + 5;
int val[MAXN], ch[MAXN][2], rnd[MAXN], siz[MAXN], tot, root;
bool rev[MAXN];

void Init() {
    root = 0, tot = 0;
}

inline void PushUp(int p) {
    siz[p] = siz[ls(p)] + siz[rs(p)] + 1;
}

inline void PushDown(int p) {
    if(rev[p]) {
        swap(ls(p), rs(p));
        if(ls(p))
            rev[ls(p)] ^= 1;
        if(rs(p))
            rev[rs(p)] ^= 1;
        rev[p] = 0;
    }
}

void SplitRank(int p, int rk, int &x, int &y) {
    if(!p) {
        x = y = 0;
        return;
    }
    PushDown(p);
    if(rk <= siz[ls(p)]) {
        y = p;
        SplitRank(ls(p), rk, x, ls(p));
        PushUp(y);
    } else {
        x = p;
        SplitRank(rs(p), rk - siz[ls(p)] - 1, rs(p), y);
        PushUp(x);
    }
}

int Merge(int x, int y) {
    if(!x || !y)
        return x | y;
    if(rnd[x] < rnd[y]) {
        PushDown(x);
        rs(x) = Merge(rs(x), y);
        PushUp(x);
        return x;
    } else {
        PushDown(y);
        ls(y) = Merge(x, ls(y));
        PushUp(y);
        return y;
    }
}

int NewNode(int v) {
    int p = ++tot;
    ch[p][0] = ch[p][1] = 0;
    val[p] = v, rnd[p] = rand();
    siz[p] = 1;
    return p;
}

void Insert(int &root, int v) {
    root = Merge(root, NewNode(v));
}

void Reverse(int &root, int l, int r) {
    int x = 0, y = 0, z = 0;
    SplitRank(root, l - 1, x, y);
    SplitRank(y, r + 1 - l, y, z);
    rev[y] ^= 1;
    root = Merge(Merge(x, y), z);
}

vector<int> ans;

void Show(int p) {
    PushDown(p);
    if(ls(p))
        Show(ls(p));
    ans.push_back(val[p]);
    if(rs(p))
        Show(rs(p));
}

int d[MAXN], f[MAXN], a[MAXN];

int u2topo[MAXN], cnttopo, topo2u[MAXN];

struct Query {
    int u, k, ans, id;
    bool operator<(const Query& q)const {
        return u2topo[u] < u2topo[q.u];
    }
} que[MAXN];

struct cmp {
    bool operator()(const Query& q1, const Query& q2)const {
        return q1.id < q2.id;
    }
};

int que2[MAXN];
int front, back;

int main() {
#ifdef Yinku
    freopen("Yinku.in", "r", stdin);
#endif // Yinku
    int n, q;
    while(~scanf("%d%d", &n, &q)) {
        Init();
        for(int i = 1; i <= n; ++i) {
            Insert(root, i);
        }
        for(int i = 1; i <= q; ++i) {
            int l, r;
            scanf("%d%d", &l, &r);
            Reverse(root, l, r);
        }
        ans.clear();
        Show(root);
        for(int i = 0; i < ans.size(); ++i)
            printf("%d%c", ans[i], " \n"[i == ans.size() - 1]);
    }
    return 0;
}