Submission #835409

#	Time	Username	Problem	Language	Result	Execution time	Memory
835409		SamAnd	Radio Towers (IOI22_towers)	C++17	23 / 100	4101 ms	8520 KiB

towers

#include "towers.h"
#include <bits/stdc++.h>
using namespace std;
#define fi first
#define se second
#define m_p make_pair
#define all(x) (x).begin(),(x).end()
#define sz(x) ((int)(x).size())
typedef long long ll;
const int N = 100005;

int n, d;
int a[N];

int ul[N], ur[N];
vector<pair<pair<int, int>, pair<int, int> > > b;

void pre()
{
    b.clear();

    vector<int> s;
    for (int i = 1; i <= n; ++i)
    {
        while (!s.empty() && a[s.back()] <= a[i])
            s.pop_back();
        s.push_back(i);

        int l = 0, r = sz(s) - 1;
        ul[i] = 0;
        while (l <= r)
        {
            int m = (l + r) / 2;
            if (a[s[m]] - d >= a[i])
            {
                ul[i] = s[m];
                l = m + 1;
            }
            else
            {
                r = m - 1;
            }
        }
    }
    s.clear();
    for (int i = n; i >= 1; --i)
    {
        while (!s.empty() && a[s.back()] <= a[i])
            s.pop_back();
        s.push_back(i);

        int l = 0, r = sz(s) - 1;
        ur[i] = n + 1;
        while (l <= r)
        {
            int m = (l + r) / 2;
            if (a[s[m]] - d >= a[i])
            {
                ur[i] = s[m];
                l = m + 1;
            }
            else
                r = m - 1;
        }
    }

    for (int i = 1; i <= n; ++i)
    {
        ul[i]++;
        ur[i]--;
    }

    for (int i = 1; i <= n; ++i)
    {
        b.push_back(m_p(m_p(ur[i] - ul[i] + 1, i), m_p(ul[i], ur[i])));
    }
    sort(all(b));
    set<int> t;
    t.insert(0);
    t.insert(n + 1);
    for (int ii = 0; ii < n; ++ii)
    {
        int i = b[ii].fi.se;
        t.insert(i);
        auto it = t.find(i);
        --it;
        if (ur[*it] < ul[i])
            b[ii].fi.fi = 1;
        else
            b[ii].fi.fi = *it + 1;
        b[ii].fi.se = i;
        ++it;
        ++it;
        b[ii].se.fi = i;
        if (ur[i] < ul[*it])
            b[ii].se.se = n;
        else
            b[ii].se.se = *it - 1;
    }
}

void init(int N, std::vector<int> H)
{
    n = N;
    for (int i = 1; i <= n; ++i)
        a[i] = H[i - 1];
}

int max_towers(int L, int R, int D)
{
    ++L;
    ++R;
    //if (b.empty())
    {
        d = D;
        pre();
    }

    int ans = 0;
    for (int i = 0; i < n; ++i)
    {
        if (b[i].fi.fi <= L && L <= b[i].fi.se && b[i].se.fi <= R && R <= b[i].se.se)
            ++ans;
    }
    return ans;
}

/*
7 1
10 20 60 40 50 30 70
0 1 17

7 3
10 20 60 40 50 30 70
1 5 10
2 2 100
0 6 17
*/

• Subtask 1: 0 / 4
• Subtask 2: 11 / 11
• Subtask 3: 12 / 12
• Subtask 4: 0 / 14
• Subtask 5: 0 / 17
• Subtask 6: 0 / 19
• Subtask 7: 0 / 23