Submission #752537

#	Time	Username	Problem	Language	Result	Execution time	Memory
752537		aryan12	Sequence (APIO23_sequence)	C++17	100 / 100	1022 ms	110704 KiB

sequence

#include "sequence.h"
#include <bits/stdc++.h>
using namespace std;
#define int long long
 
const int N = 5e5 + 5, INF = 1e18;

struct segtree
{
    pair<int, int> seg[N * 4];
    int lazy[N * 4];

    void Build(int l, int r, int pos)
    {
        seg[pos] = {-r, -l};
        if(l == r) return;
        int mid = (l + r) / 2;
        Build(l, mid, pos * 2);
        Build(mid + 1, r, pos * 2 + 1);
    }

    void UpdateLazy(int l, int r, int pos)
    {
        if(l == r)
        {
            seg[pos].first += lazy[pos];
            seg[pos].second += lazy[pos];
            lazy[pos] = 0;
            return;
        }
        seg[pos].first += lazy[pos];
        seg[pos].second += lazy[pos];
        lazy[pos * 2] += lazy[pos];
        lazy[pos * 2 + 1] += lazy[pos];
        lazy[pos] = 0;
    }

    void Update(int l, int r, int pos, int ql, int qval)
    {
        if(lazy[pos] != 0)
        {
            UpdateLazy(l, r, pos);
        }
        if(ql > r)
        {
            // cout << "Update(" << l << ", " << r << ") out of bounds\n";
            return;
        }
        if(l == r)
        {
            // cout << "Update(" << l << ", " << r << ") total in [1]\n";
            seg[pos].first += qval;
            seg[pos].second += qval;
            return;
        }
        if(l >= ql)
        {
            // cout << "Update(" << l << ", " << r << ") total in [2]\n";
            seg[pos].first += qval;
            seg[pos].second += qval;
            lazy[pos * 2] += qval;
            lazy[pos * 2 + 1] += qval;
            return;
        }
        int mid = (l + r) / 2;
        Update(l, mid, pos * 2, ql, qval);
        Update(mid + 1, r, pos * 2 + 1, ql, qval);
        // cout << "Update(" << l << ", " << r << ") partial\n";
        seg[pos].first = min(seg[pos * 2].first, seg[pos * 2 + 1].first);
        seg[pos].second = max(seg[pos * 2].second, seg[pos * 2 + 1].second);
    }

    pair<int, int> Query(int l, int r, int pos, int ql, int qr)
    {
        if(lazy[pos] != 0)
        {
            UpdateLazy(l, r, pos);
        }
        if(ql <= l && r <= qr)
        {
            return seg[pos];
        }
        if(ql > r || l > qr)
        {
            return {INF, -INF};
        }
        int mid = (l + r) / 2;
        pair<int, int> p1 = Query(l, mid, pos * 2, ql, qr);
        pair<int, int> p2 = Query(mid + 1, r, pos * 2 + 1, ql, qr);
        return {min(p1.first, p2.first), max(p1.second, p2.second)};
    }
} before, after;


int32_t sequence(int32_t n, vector<int32_t> a) 
{
    before.Build(1, n, 1);
    after.Build(1, n, 1);
    vector<int> occ[n + 1];
    for(int i = 0; i < a.size(); i++)
    {
        occ[a[i]].push_back(i + 1);
    }
    int ans = 1;
    for(int i = 1; i <= n; i++)
    {
        // cout << "i = " << i << endl;
        for(int j: occ[i])
        {
            // cout << "hello" << endl;
            before.Update(1, n, 1, j, 2);
        }
        for(int l = 0; l < occ[i].size(); l++)
        {
            int r = l + ans;
            if(r >= occ[i].size())
            {
                break;
            }
            int afterRightMin = after.Query(1, n, 1, occ[i][r], n).first;
            int afterLeftMax = after.Query(1, n, 1, 1, occ[i][l] - 1).second;
            afterLeftMax = max(afterLeftMax, 0LL);
            
            int beforeRightMax = before.Query(1, n, 1, occ[i][r], n).second;
            int beforeLeftMin = before.Query(1, n, 1, 1, occ[i][l] - 1).first;
            beforeLeftMin = min(beforeLeftMin, 0LL);

            int afterAnswer = afterRightMin - afterLeftMax;
            int beforeAnswer = beforeRightMax - beforeLeftMin;

            // cout << beforeLeftMin << " " << afterLeftMax << " " << afterRightMin << " " << beforeRightMax << "\n";

            if(afterAnswer <= 0 && beforeAnswer >= 0)
            {
                ans += 1;
                l -= 1;
            }
        }
        for(int j: occ[i])
        {
            after.Update(1, n, 1, j, 2);
        }
    }
    return ans;
}

Compilation message (stderr)

sequence.cpp: In function 'int32_t sequence(int32_t, std::vector<int>)':
sequence.cpp:100:22: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  100 |     for(int i = 0; i < a.size(); i++)
      |                    ~~^~~~~~~~~~
sequence.cpp:113:26: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  113 |         for(int l = 0; l < occ[i].size(); l++)
      |                        ~~^~~~~~~~~~~~~~~
sequence.cpp:116:18: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  116 |             if(r >= occ[i].size())
      |                ~~^~~~~~~~~~~~~~~~

• 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