Submission #752335

#	Time	Username	Problem	Language	Result	Execution time	Memory
752335		aryan12	Sequence (APIO23_sequence)	C++17	0 / 100	95 ms	6116 KiB

sequence

#include "sequence.h"
#include <bits/stdc++.h>
using namespace std;
#define int long long
 
const int N = 5e5 + 5, INF = 1e18;
int seg[N * 2 * 4];

int32_t print_occ(int val, vector<int32_t> &x)
{
    int ans = 0;
    for(int i: x)
    {
        ans += (i == val);
    }
    return ans;
}

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

void Update(int l, int r, int pos, int qpos, int qval)
{
    if(l == r)
    {
        seg[pos] = min(seg[pos], qval);
        return;
    }
    int mid = (l + r) / 2;
    if(qpos <= mid)
    {
        Update(l, mid, pos * 2, qpos, qval);
    }
    else
    {
        Update(mid + 1, r, pos * 2 + 1, qpos, qval);
    }
    seg[pos] = min(seg[pos * 2], seg[pos * 2 + 1]);
}

int Query(int l, int r, int pos, int ql, int qr)
{
    if(ql <= l && r <= qr)
    {
        return seg[pos];
    }
    if(ql > r || l > qr)
    {
        return INF;
    }
    int mid = (l + r) / 2;
    return min(Query(l, mid, pos * 2, ql, qr), Query(mid + 1, r, pos * 2 + 1, ql, qr));
}
 
int32_t sequence(int32_t n, vector<int32_t> a) 
{
    vector<int32_t> b = a;
    sort(b.begin(), b.end());
    int median1 = (n - 1) / 2, median2 = n / 2;
    if(b[median1] != 2)
    {
        return print_occ(b[median1], b);
    }
    if(b[median2] != 2)
    {
        return print_occ(b[median2], b);
    }
    int ans = print_occ(b[median2], b);
    for(int check = 1; check <= 3; check += 2)
    {
        vector<int> pref(n, 0);
        Build(0, 2 * n, 1);
        int cur_cnt = n;
        for(int i = 0; i < n; i++)
        {
            cur_cnt = (a[i] == check) ? cur_cnt + 1 : cur_cnt - 1;
            pref[i] = (i == 0) ? 0 : pref[i - 1];
            if(a[i] == check)
            {
                pref[i] += 1;
            }
            Update(0, 2 * n, 1, cur_cnt, i);
            int min_ans = Query(0, 2 * n, 1, 0, cur_cnt);
            if(min_ans == INF)
            {
                continue;
            }
            int this_ans = (min_ans == 0) ? pref[i] : pref[i] - pref[min_ans - 1];
            ans = max(ans, this_ans);
        }
    }
    return ans;
}

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