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# 洛谷P4146 序列终结者 题解 splay tree

• 区间更新（+x）
• 区间翻转
• 区间查询（最大值）

``````#include <bits/stdc++.h>
using namespace std;
#define int long long
const int maxn = 1e5 + 5;
const int INF = (1LL<<60);

int n, m;
struct Node {
int s[2], p, v;

Node() {};
Node(int _v, int _p) {v = _v; p = _p; s[0] = s[1] = 0; flag = 0; sz = 1; mx = v; add = 0;}
} tr[maxn];
int root, idx;

void push_up(int x) {
tr[x].sz = tr[tr[x].s[0]].sz + tr[tr[x].s[1]].sz + 1;
tr[x].mx = max(tr[x].v, max(tr[tr[x].s[0]].mx, tr[tr[x].s[1]].mx));
}

void t_swap(int x) {
tr[x].flag ^= 1;
swap(tr[x].s[0], tr[x].s[1]);
}

void t_add(int x, int d) {
tr[x].v += d;
tr[x].mx += d;
}

void push_down(int x) {
if (tr[x].flag) {
t_swap(tr[x].s[0]);
t_swap(tr[x].s[1]);
tr[x].flag = 0;
}
}
}

void f_s(int p, int u, bool k) {
tr[p].s[k] = u;
tr[u].p = p;
}

void rot(int x) {
int y = tr[x].p, z = tr[y].p;
bool k = tr[y].s[1] == x;
f_s(z, x, tr[z].s[1]==y);
f_s(y, tr[x].s[k^1], k);
f_s(x, y, k^1);
push_up(y), push_up(x);
}

void splay(int x, int k) {
while (tr[x].p != k) {
int y = tr[x].p, z = tr[y].p;
if (z != k)
(tr[y].s[1]==x) ^ (tr[z].s[1]==y) ? rot(x) : rot(y);
rot(x);
}
if (!k) root = x;
}

int get_k(int k) {
int u = root;
while (u) {
push_down(u);
if (tr[tr[u].s[0]].sz >= k) u = tr[u].s[0];
else if (tr[tr[u].s[0]].sz + 1 == k) return u;
else k -= tr[tr[u].s[0]].sz + 1, u = tr[u].s[1];
}
return -1;
}

int build(int l, int r, int p) {
int x = ++idx;
int v = (l < 1 || l > n) ? -INF : 0;
tr[x] = Node(v, p);
int mid = (l + r) / 2;
if (l < mid) tr[x].s[0] = build(l, mid-1, x);
if (r > mid) tr[x].s[1] = build(mid+1, r, x);
push_up(x);
return x;
}

void init() {
tr[0] = Node(0, 0);
tr[0].sz = 0;
tr[0].mx = -INF;
}

signed main() {
init();
cin >> n >> m;
root = build(0, n+1, 0);
while (m--) {
int op, l, r, x;
cin >> op >> l >> r;
l = get_k(l), r = get_k(r+2);
splay(l, 0), splay(r, l);
push_down(l), push_down(r);
if (op == 1) {
cin >> x;