Submission #1220030

#	Time	Username	Problem	Language	Result	Execution time	Memory
1220030		Ghulam_Junaid	Event Hopping (BOI22_events)	C++20	100 / 100	233 ms	25192 KiB

events

#include <bits/stdc++.h>
using namespace std;

const int N = 1e5 + 10, LG = 18;
int n, q, par[N][LG], a[N][2], seg[8 * N], who[2 * N];
map<int, int> mp;
vector<int> vec;
vector<pair<int, int>> points;
vector<pair<pair<int, int>, int>> srt;

void modify(int p, int x, int v = 1, int s = 0, int e = 2 * n){
    if (e - s == 1){
        seg[v] = min(seg[v], x);
        return ;
    }

    int mid = (s + e) / 2, lc = 2 * v, rc = lc + 1;

    if (p < mid) modify(p, x, lc, s, mid);
    else modify(p, x, rc, mid, e);

    seg[v] = min(seg[lc], seg[rc]);
}

int get(int l, int r, int v = 1, int s = 0, int e = 2 * n){
    if (r <= s || e <= l) return 1e9;
    if (l <= s && e <= r) return seg[v];

    int mid = (s + e) / 2, lc = 2 * v, rc = lc + 1;
    return min(get(l, r, lc, s, mid), get(l, r, rc, mid, e));
}

int main(){
    ios::sync_with_stdio(0);
    cin.tie(0); cout.tie(0);
    memset(par, -1, sizeof par);
    memset(seg, 31, sizeof seg);

    cin >> n >> q;
    for (int i = 0; i < n; i ++){
        int s, e;
        cin >> s >> e;
        points.push_back({s, e});
        vec.push_back(s);
        vec.push_back(e);
    }
    sort(vec.begin(), vec.end());
    vec.resize(unique(vec.begin(), vec.end()) - vec.begin());

    for (int i = 0; i < vec.size(); i ++)
        mp[vec[i]] = i;
    for (int i = 0; i < n; i ++)
        points[i].first = mp[points[i].first], points[i].second = mp[points[i].second];
    
    for (int i = 0; i < n; i ++)
        srt.push_back({{points[i].second, points[i].first}, i});
    sort(srt.begin(), srt.end());

    for (int i = 0; i < n; i ++){
        auto [P, id] = srt[i];
        auto [e, s] = P;
        modify(e, s);
        who[s] = id;
        int mn = get(s, e + 1);
        if (mn != s)
            par[id][0] = who[mn];
    }

    for (int j = 1; j < LG; j ++)
        for (int i = 0; i < n; i ++)
            if (par[i][j - 1] != -1)
                par[i][j] = par[par[i][j - 1]][j - 1];

    for (int i = 0; i < q; i ++){
        int l, r;
        cin >> l >> r;
        l--, r--;

        if (points[r].second < points[l].second){
            cout << "impossible\n";
            continue;
        }

        if (points[r].second == points[l].second){
            cout << 1 - (l == r) << '\n';
            continue;
        }

        if (points[r].first <= points[l].second){
            cout << "1\n";
            continue;
        }

        int cur = r, ans = 0;
        for (int j = LG - 1; j >= 0; j --){
            if (par[cur][j] == -1) continue;
            if (points[par[cur][j]].first > points[l].second)
                cur = par[cur][j], ans += (1 << j);
        }

        if (par[cur][0] == -1){
            cout << "impossible\n";
            continue;
        }

        cout << ans + 2 << '\n';
    }
}

• Subtask 1: 10 / 10
• Subtask 2: 10 / 10
• Subtask 3: 15 / 15
• Subtask 4: 15 / 15
• Subtask 5: 20 / 20
• Subtask 6: 30 / 30