【BZOJ 1251】序列终结者

Splay的序列操作
注意：
更新的时候，要先确定子树不为空在进行更新。
空指针的mx值要设为-inf

#include <cstdio>#include <iostream>#include <algorithm>using namespace std;const int maxn = 50010;struct node{    int num, val, size, turn, mx, add;    node *pre, *ch[2];    void update(){        size = ch[0]->size + ch[1]->size + 1;        mx = max(max(ch[0]->mx, ch[1]->mx), val);    }    int wh(){return pre->ch[0] == this ? 0 : 1;}    void set_ch(int wh, node *child);}pool[maxn], *root, *null;void node::set_ch(int wh, node *child){    ch[wh] = child;    if(child != null) child->pre = this;    update();}int cnt, n, m;node *get(int num, int val){    node *now = &pool[++cnt];    now->mx = now->val = val, now->num = num, now->size = 1;    now->pre = now->ch[0] = now->ch[1] = null;    now->turn = now->add = 0;    return now;}void down(node *now){    if(now->add != 0){        if(now->ch[0] != null) {            now->ch[0]->add += now->add;            now->ch[0]->mx += now->add;            now->ch[0]->val += now->add;        }        if(now->ch[1] != null){            now->ch[1]->add += now->add;            now->ch[1]->mx += now->add;            now->ch[1]->val += now->add;        }        now->add = 0;    }    if(now->turn != 0){        now->turn = 0;        swap(now->ch[0]->ch[0], now->ch[0]->ch[1]);        swap(now->ch[1]->ch[0], now->ch[1]->ch[1]);        now->ch[0]->turn ^= 1;        now->ch[1]->turn ^= 1;    }}node *find(int num){    node *now = root;    int rank = num;    while(now != null){        down(now);        if(now->ch[0]->size+1 == rank) return now;        else if(now->ch[0]->size+1 < rank){            rank -= now->ch[0]->size+1;            now = now->ch[1];        }else now = now->ch[0];    }    return null;}void rotate(node *now){    node *fa = now->pre, *gra = now->pre->pre;    int wh = now->wh();    fa->set_ch(wh, now->ch[wh^1]);    now->set_ch(wh^1, fa);    now->pre = gra;    if(gra != null) gra->ch[gra->ch[0] == fa ? 0 : 1] = now;}void splay(node *now, node *tar){    for( ; now->pre != tar; rotate(now))        if(now->pre->pre != tar)            now->wh() == now->pre->wh() ? rotate(now->pre) : rotate(now);     if(tar == null) root = now;}void insert(int num, int val){    node *now = root, *last = null;    while(now != null){        last = now;        if(now->num > num) now = now->ch[0];        else now = now->ch[1];    }    now = get(num, val);    if(last == null) root = now;    else{        if(num < last->num) last->set_ch(0, now);        else last->set_ch(1, now);        splay(now, null);    }}int main(){    null = pool;    null->add = null->num = 0, null->mx = -2e9;    null->turn = null->size = null->val = 0;    null->ch[0] = null->ch[1] = null->pre = null;    root = null;    scanf("%d%d", &n, &m);    insert(0, 0), insert(n+1, 0);    for(int i = 1; i <= n; i ++) insert(i, 0);    for(int i = 1; i <= m; i ++){        int a, b, c, d;        scanf("%d%d%d", &a, &b, &c);        if(a == 1){            scanf("%d", &d);            node *l = find(b), *r = find(c+2);            splay(r, null), splay(l, r);            l->ch[1]->add += d;            l->ch[1]->val += d;            l->ch[1]->mx += d;        }else if(a == 2){            node *l = find(b), *r = find(c+2);            splay(r, null), splay(l, r);            l->ch[1]->turn ^= 1;            swap(l->ch[1]->ch[0], l->ch[1]->ch[1]);        }else{            node *l = find(b), *r = find(c+2);            splay(r, null), splay(l, r);            printf("%d\n", l->ch[1]->mx);        }    }    return 0;}