Submission #884126

#	Time	Username	Problem	Language	Result	Execution time	Memory
884126		nguyentunglam	Sequence (APIO23_sequence)	C++17	100 / 100	1125 ms	58564 KiB

sequence

#include<bits/stdc++.h>
#define fi first
#define se second
#define endl "\n"
#define ii pair<int, int>
using namespace std;
const int N = 5e5 + 10;

vector<int> pos[N];

int L[N], R[N];

int minx[N << 2], maxx[N << 2], lazy[N << 2];

int st[N], idx[N];

void push(int s, int l, int r) {
  if (!lazy[s]) return;
  minx[s] += lazy[s];
  maxx[s] += lazy[s];
  if (l != r) {
    lazy[s << 1] += lazy[s];
    lazy[s << 1 | 1] += lazy[s];
  }
  lazy[s] = 0;
}

void up(int s, int l, int r, int from, int to, int val) {
  push(s, l, r);
  if (l > to || r < from) return;
  if (from <= l && r <= to) {
    lazy[s] = val;
    push(s, l, r);
    return;
  }
  int mid = l + r >> 1;
  up(s << 1, l, mid, from, to, val);
  up(s << 1 | 1, mid + 1, r, from, to, val);
  minx[s] = min(minx[s << 1], minx[s << 1 | 1]);
  maxx[s] = max(maxx[s << 1], maxx[s << 1 | 1]);
}

int get_min(int s, int l, int r, int from, int to) {
  push(s, l, r);
  if (l > to || r < from) return 1e9;
  if (from <= l && r <= to) return minx[s];
  int mid = l + r >> 1;
  return min(get_min(s << 1, l, mid, from, to), get_min(s << 1 | 1, mid + 1, r, from, to));
}
int get_max(int s, int l, int r, int from, int to) {
  push(s, l, r);
  if (l > to || r < from) return -1e9;
  if (from <= l && r <= to) return maxx[s];
  int mid = l + r >> 1;
  return max(get_max(s << 1, l, mid, from, to), get_max(s << 1 | 1, mid + 1, r, from, to));
}

int sequence(int n, vector<int> a) {
    int ans = 1;

    a.insert(a.begin(), 0);

    for(int i = 1; i <= n; i++) pos[a[i]].push_back(i);

    for(int i = 1; i <= n; i++) up(1, 0, n, i, i, -i);

    for(int val = 1; val <= n; val++) {
      int pre = 0;
      int j = 0, k = 0;
      st[0] = 1e9;
      for(int i = 0; i < pos[val].size(); i++) {
        int cur = pos[val][i];
        L[i] = get_min(1, 0, n, 0, cur - 1);
        R[i] = get_max(1, 0, n, 0, cur - 1);
        int from = get_min(1, 0, n, cur, n);
        int to = get_max(1, 0, n, cur, n);

        while (j <= i && L[j] > to || R[j] < from) {
          if (L[j] + j * 2 <= st[k]) {
            ++k;
            st[k] = L[j] + j * 2;
            idx[k] = j;
          }
          j++;
        }


        if (j > 0 && L[j - 1] > to) {

          int l = 1, r = k, last = 0;
          while (l <= r) {
            int mid = l + r >> 1;
            if (to + (i + 1) * 2 >= st[mid]) {
              last = mid;
              r = mid - 1;
            } else l = mid + 1;
          }
          if (last) ans = max(ans, i - idx[last] + 1);
        }

        ans = max(ans, i - j + 1);
      }
      for(int &j : pos[val]) up(1, 0, n, j, n, 2);
    }
    return ans;
}

#ifdef ngu
int main() {

    freopen ("task.inp", "r", stdin);
    freopen ("task.out", "w", stdout);

    int n; cin >> n;
    vector<int> a(n);
    for(int i = 0; i < n; i++) cin >> a[i];
    cout << sequence(n, a);

////    cout << sequence(7, {1, 2, 3, 1, 2, 1, 3});
////    cout << sequence(9, {1, 1, 2, 3, 4, 3, 2, 1, 1});
//    cout << sequence(14, {2, 6, 2, 5, 3, 4, 2, 1, 4, 3, 5, 6, 3, 2});

}
#endif // ngu

Compilation message (stderr)

sequence.cpp: In function 'void up(int, int, int, int, int, int)':
sequence.cpp:36:15: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
   36 |   int mid = l + r >> 1;
      |             ~~^~~
sequence.cpp: In function 'int get_min(int, int, int, int, int)':
sequence.cpp:47:15: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
   47 |   int mid = l + r >> 1;
      |             ~~^~~
sequence.cpp: In function 'int get_max(int, int, int, int, int)':
sequence.cpp:54:15: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
   54 |   int mid = l + r >> 1;
      |             ~~^~~
sequence.cpp: In function 'int sequence(int, std::vector<int>)':
sequence.cpp:71:24: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   71 |       for(int i = 0; i < pos[val].size(); i++) {
      |                      ~~^~~~~~~~~~~~~~~~~
sequence.cpp:78:23: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
   78 |         while (j <= i && L[j] > to || R[j] < from) {
      |                ~~~~~~~^~~~~~~~~~~~
sequence.cpp:92:25: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
   92 |             int mid = l + r >> 1;
      |                       ~~^~~
sequence.cpp:68:11: warning: unused variable 'pre' [-Wunused-variable]
   68 |       int pre = 0;
      |           ^~~

• 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