Submission #959844

#	Time	Username	Problem	Language	Result	Execution time	Memory
959844		kilkuwu	Sequence (APIO23_sequence)	C++17	100 / 100	731 ms	58648 KiB

sequence

#include "sequence.h"

#include <bits/stdc++.h>

#ifdef LOCAL
#include "template/dbgnc.hpp"
#else
#define dbg(...) ;
#define timer(...) ;
#endif

struct Tag {
  int add = 0;

  void apply(const Tag& t) {
    add += t.add;
  }
};

struct Info {
  int mn = 0, mx = 0;  

  void apply(const Tag& t) {
    mn += t.add, mx += t.add;
  }
};

Info operator+(const Info& a, const Info& b) {
  return {std::min(a.mn, b.mn), std::max(a.mx, b.mx)};
}

struct SegmentTree {
  int n;
  std::vector<Info> info;
  std::vector<Tag> tag;

  SegmentTree(int _n) : n(_n), info(4 * n), tag(4 * n) {}

  void apply(int k, const Tag& t) {
    info[k].apply(t);
    tag[k].apply(t);
  }
  
  void push(int k) {
    apply(k * 2, tag[k]);
    apply(k * 2 + 1, tag[k]);
    tag[k] = Tag();
  }

  void update(int k, int l, int r, int ql, int qr, const Tag& t) {
    if (l > qr || r < ql) return;
    if (ql <= l && r <= qr) {
      info[k].apply(t);
      tag[k].apply(t);
      return;
    }

    push(k);

    int mid = (l + r) / 2;
    update(k * 2, l, mid, ql, qr, t);
    update(k * 2 + 1, mid + 1, r, ql, qr, t);
    info[k] = info[k * 2] + info[k * 2 + 1];
  }

  Info query(int k, int l, int r, int ql, int qr) {
    if (l > qr || r < ql) return {(int) 1e9, (int) -1e9};
    if (ql <= l && r <= qr) {
      return info[k];
    }

    push(k);
    int mid = (l + r) / 2;
    return query(k * 2, l, mid, ql, qr) + query(k * 2 + 1, mid + 1, r, ql, qr);
  }

  void update(int l, int r, const Tag& t) {
    update(1, 0, n - 1, l, r, t);
  }

  Info query(int l, int r) {
    return query(1, 0, n - 1, l, r);
  }
};

int sequence(int N, std::vector<int> A) {
  std::vector<std::vector<int>> pos(N);

  for (int i = 0; i < N; i++) {
    pos[--A[i]].push_back(i);
  }

  SegmentTree tree(N + 1);
  for (int i = 0; i < N; i++) {
    tree.update(i + 1, N, {1});
  }

  int ans = 1;

  for (int v = 0; v < N; v++) {
    for (int i : pos[v]) {
      tree.update(i + 1, N, {-2});
    }

    int sz = pos[v].size();

    for (int i = sz - 1; i >= 0; i--) {
      int l = pos[v][i];
      tree.update(l + 1, N, {2});
      while (i + ans < sz) {
        int mid = ans + 1;
        int r = pos[v][i + mid - 1];
        auto rl = tree.query(0, l);
        int l1 = rl.mn, r1 = rl.mx;
        auto rr = tree.query(r + 1, N);
        int l2 = rr.mn - 2 * mid, r2 = rr.mx;

        if (std::max(l1, l2) <= std::min(r1, r2)) {
          ans++;
        } else {
          break;
        }
      }
    }

    for (int i : pos[v]) {
      tree.update(i + 1, N, {-2});  // becomes -1
    }
  }

  return ans;
}

#ifdef LOCAL
int main() {
  int N;
  assert(1 == scanf("%d", &N));

  std::vector<int> A(N);
  for (int i = 0; i < N; ++i) {
    assert(1 == scanf("%d", &A[i]));
  }

  int result = sequence(N, A);
  printf("%d\n", result);
  return 0;
}

#endif

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