UVA - 11922 Permutation Transformer——splay分裂合并

注意spaly的时候pushdown两遍，注意建立虚拟节点

#include 
const int maxn = 1e5 + 10;
using namespace std;
struct Node {
    Node *ch[2];
    int v, s, lazy;
    Node() { ch[0] = ch[1] = NULL; v = s = lazy = 0; }
    int cmp(int x) { if (x == ch[0]->s+1) return -1; return x < ch[0]->s+1 ? 0 : 1; }
    void maintain() { s = ch[0]->s+ch[1]->s+1; }
    void pushdown() {
        if (!lazy) return;
        swap(ch[0], ch[1]);
        ch[0]->lazy = !(ch[0]->lazy);
        ch[1]->lazy = !(ch[1]->lazy);
        lazy = 0;
    }
};
Node *null = new Node();
Node *newnode(int v) {
    Node *node = new Node();
    node->ch[0] = node->ch[1] = null;
    node->v = v;
    node->s = 1;
    node->lazy = 0;
    return node;
}
void rotate(Node *&o, int d) {
    Node *k = o->ch[d^1]; o->ch[d^1] = k->ch[d]; k->ch[d] = o;
    o->maintain(); k->maintain(); o = k;
}
void splay(Node *&o, int k) {
    o->pushdown();
    int d = o->cmp(k);
    if (d == 1) k -= o->ch[0]->s + 1;
    if (d != -1) {
        Node *p = o->ch[d];
        p->pushdown();
        int d2 = p->cmp(k);
        int k2 = (d2 == 0 ? k : k - p->ch[0]->s - 1);
        if (d2 != -1) {
            splay(p->ch[d2], k2);
            if (d == d2) rotate(o, d^1); else rotate(o->ch[d], d);
        }
        rotate(o, d^1);
    }
}
Node *merge(Node *left, Node *right) {
    splay(left, left->s);
    left->ch[1] = right;
    left->maintain();
    return left;
}
void split(Node *o, int k, Node *&left, Node *&right) {
    splay(o, k);
    left = o;
    right = o->ch[1];
    o->ch[1] = null;
    left->maintain();
}
Node *root;
void init() { root = newnode(0); }
void build(Node *&o, int l, int r) {
    if (l > r) return;
    int mid = (l + r)>>1;
    o = newnode(mid);
    build(o->ch[0], l, mid-1);
    build(o->ch[1], mid+1, r);
    o->maintain();
}
void output(Node *o) {
    if (o == null) return;
    o->pushdown();
    output(o->ch[0]);
    if (o->v != 0) printf("%d\n", o->v);
    output(o->ch[1]);
}
int n, m;
int main() {
    scanf("%d%d", &n, &m);
    init();
    build(root->ch[1], 1, n);
    root->maintain();
    while (m--) {
        int a, b;
        scanf("%d%d", &a, &b);
        Node *left, *right, *mid, *t;
        split(root, a, left, t);
        split(t, b-a+1, mid, right);
        mid->lazy ^= 1;
        root = merge(merge(left, right), mid);
    }
    output(root);
    return 0;
}