luogu P4146 序列终结者

嘟嘟嘟

这是一道splay基础题。

最坑的一点是，因为有些节点可能没有左儿子或右儿子，所以必须把t[0].Max赋成-INF！

因为这个调了半天，看来回头复习复习splay是对的……

#include<cstdio>
#include<iostream>
#include<cmath>
#include<algorithm>
#include<cstring>
#include<cstdlib>
#include<cctype>
#include<vector>
#include<stack>
#include<queue>
using namespace std;
#define enter puts("")
#define space putchar(' ')
#define Mem(a, x) memset(a, x, sizeof(a))
#define In inline
typedef long long ll;
typedef double db;
const int INF = 0x3f3f3f3f;
const db eps = 1e-8;
const int maxn = 5e4 + 5;
inline ll read()
{
  ll ans = 0;
  char ch = getchar(), last = ' ';
  while(!isdigit(ch)) last = ch, ch = getchar();
  while(isdigit(ch)) ans = (ans << 1) + (ans << 3) + ch - '0', ch = getchar();
  if(last == '-') ans = -ans;
  return ans;
}
inline void write(ll x)
{
  if(x < 0) x = -x, putchar('-');
  if(x >= 10) write(x / 10);
  putchar(x % 10 + '0');
}int n, m, a[maxn];
struct Tree
{
  int ch[2], fa;
  int val, siz, Max;
  int add, rev;
}t[maxn];
int root, tcnt = 0;In void _PrintTr(int now)
{
  if(!now) return;
  printf("now:%d val:%d Max:%d ls:%d rs:%d\n", now, t[now].val, t[now].Max, t[now].ch[0], t[now].ch[1]);
  _PrintTr(t[now].ch[0]); _PrintTr(t[now].ch[1]);
}
void _Travel(int now, int dep)
{
  if(t[now].ch[1]) _Travel(t[now].ch[1], dep + 1);
  for(int i = 1; i < dep; ++i) putchar('\t');
  printf("\033[36m%d %d\033[0m\n", t[now].val, t[now].Max);
  if(t[now].ch[0]) _Travel(t[now].ch[0], dep + 1);}In void c_rev(int now)
{
  swap(t[now].ch[0], t[now].ch[1]);
  t[now].rev ^= 1;
}
In void c_add(int now, int lzy)
{
  t[now].val += lzy; t[now].Max += lzy;
  t[now].add += lzy;
}
In void pushdown(int now)
{
  if(t[now].rev)
    {
      if(t[now].ch[0]) c_rev(t[now].ch[0]);
      if(t[now].ch[1]) c_rev(t[now].ch[1]);
      t[now].rev = 0;
    }
  if(t[now].add)
    {
      if(t[now].ch[0]) c_add(t[now].ch[0], t[now].add);
      if(t[now].ch[1]) c_add(t[now].ch[1], t[now].add);
      t[now].add = 0;
    }
}
In void pushup(int now)
{
  t[now].siz = t[t[now].ch[0]].siz + t[t[now].ch[1]].siz + 1;
  t[now].Max = max(max(t[t[now].ch[0]].Max, t[t[now].ch[1]].Max), t[now].val);
}
In void rotate(int x)
{
  int y = t[x].fa, z = t[y].fa, k = (t[y].ch[1] == x);
  t[z].ch[t[z].ch[1] == y] = x; t[x].fa = z;
  t[y].ch[k] = t[x].ch[k ^ 1]; t[t[x].ch[k ^ 1]].fa = y;
  t[x].ch[k ^ 1] = y; t[y].fa = x;
  pushup(y), pushup(x);
}
In void splay(int x, int s)
{
  while(t[x].fa != s)
    {
      int y = t[x].fa, z = t[y].fa;
      if(z != s) rotate(((t[y].ch[0] == x) ^ (t[z].ch[0] == y)) ? x : y);
      rotate(x);
    }
  if(!s) root = x;
}In int build(int L, int R, int _f)
{
  if(L > R) return 0;
  int mid = (L + R) >> 1, now = ++tcnt;
  t[now].fa = _f;
  t[now].Max = t[now].val = a[mid];
  t[now].ch[0] = build(L, mid - 1, now);
  t[now].ch[1] = build(mid + 1, R, now);
  pushup(now);
  return now;
}
In int getRank(int k)
{
  int now = root;
  while(1)
    {
      pushdown(now);
      if(t[t[now].ch[0]].siz >= k) now = t[now].ch[0];
      else if(t[t[now].ch[0]].siz + 1 == k) return now;
      else k -= (t[t[now].ch[0]].siz + 1), now = t[now].ch[1];
    }
}
In void split(int L, int R)
{
  int a = getRank(L - 1), b = getRank(R + 1);
  splay(a, 0); splay(b, a);
  pushdown(root), pushdown(t[root].ch[1]);
}int main()
{
  n = read(); m = read();
  a[1] = -INF; a[n + 2] = -INF;
  root = build(1, n + 2, 0);
  t[0].Max = -INF;
  for(int i = 1; i <= m; ++i)
    {
      int op = read(), L = read() + 1, R = read() + 1, v;
      split(L, R);
      if(op == 1) v = read(), c_add(t[t[root].ch[1]].ch[0], v), pushup(t[root].ch[1]), pushup(root);
      else if(op == 2) c_rev(t[t[root].ch[1]].ch[0]), pushup(t[root].ch[1]), pushup(root);
      else write(t[t[t[root].ch[1]].ch[0]].Max), enter;
    }
  return 0;
}