Submission #1201126

#	Time	Username	Problem	Language	Result	Execution time	Memory
1201126		aykhn	Sequence (APIO23_sequence)	C++20	20 / 100	821 ms	52248 KiB

sequence

#include "sequence.h"
#include <bits/stdc++.h>

using namespace std;

struct DATA
{
  int s = 0, mxp = 0, mxs = 0, mnp = 0, mns = 0;
};

const int MXN = 5e5 + 5;

DATA st[MXN << 2];

DATA combine(DATA x, DATA y)
{
  return {x.s + y.s, max(x.mxp, x.s + y.mxp), max(y.mxs, y.s + x.mxs), min(x.mnp, x.s + y.mnp), min(y.mns, y.s + x.mns)};
}
void upd(int l, int r, int x, int ind, int val)
{
  if (l == r)
  {
    st[x] = {val, max(0, val), max(0, val), min(0, val), min(0, val)};
    return;
  }
  int mid = (l + r) >> 1;
  if (ind <= mid) upd(l, mid, 2*x, ind, val);
  else upd(mid + 1, r, 2*x + 1, ind, val);
  st[x] = combine(st[2*x], st[2*x + 1]);
}
DATA get(int l, int r, int x, int lx, int rx)
{
  if (lx > rx) return {0, 0, 0, 0, 0};
  if (l > rx || r < lx) return {0, 0, 0, 0, 0};
  if (l >= lx && r <= rx) return st[x];
  int mid = (l + r) >> 1;
  return combine(get(l, mid, 2*x, lx, rx), get(mid + 1, r, 2*x + 1, lx, rx));
}

int sequence(int N, vector<int> A)
{
  vector<int> idx[N + 1];
  for (int i = 0; i < N; i++) idx[A[i]].push_back(i);
  for (int i = 0; i < N; i++) upd(0, N - 1, 1, i, 1);
  int res = 0;
  for (int val = 1; val <= N; val++)
  {
    vector<int> &v = idx[val];
    for (int &i : v) upd(0, N - 1, 1, i, 0);
    for (int r = 0, l = 0; r < v.size(); r++)
    {
      while (l <= r)
      {
        DATA x = get(0, N - 1, 1, v[l], v[r]);
        // A = a, B = x - y
        int A = r - l + 1;
        int B = x.s;
        DATA L = get(0, N - 1, 1, 0, v[l] - 1);
        DATA R = get(0, N - 1, 1, v[r], N - 1);
        int mn = B + L.mns + R.mnp, mx = B + L.mxs + R.mxp;
        if ((mn <= 0 && 0 <= mx) || min(abs(mn), abs(mx)) <= A) 
        {
          res = max(res, A);
          break;
        }
        l++;
      }
    }
    for (int &i : v) upd(0, N - 1, 1, i, -1);
  }
  return res;
}

/*
9
1 1 2 3 4 3 2 1 1
*/

• Subtask 1: 0 / 11
• Subtask 2: 0 / 17
• Subtask 3: 7 / 7
• Subtask 4: 0 / 12
• Subtask 5: 13 / 13
• Subtask 6: 0 / 22
• Subtask 7: 0 / 18