Submission #576686

#	Time	Username	Problem	Language	Result	Execution time	Memory
576686		InternetPerson10	Event Hopping (BOI22_events)	C++17	100 / 100	785 ms	61152 KiB

events

#include <bits/stdc++.h>
typedef long long ll;

using namespace std;

set<int> s;
map<int, int> idx;
map<pair<int, int>, int> toEvent;
vector<pair<int, int>> p;
vector<int> mini;
vector<int> mo;
int point[200001][20];

int getPoint(int y2, int mid) {
    for(int i = 0; i < 20; i++) {
        if(mid & (1 << i)) {
            y2 = point[y2][i];
        }
    }
    return y2;
}

struct SegTree {
    int lx, rx;
    int val = 1e9, id = -1;
    SegTree *ls, *rs;
    SegTree(int l, int r) {
        lx = l;
        rx = r;
        if(rx - lx > 1) {
            int mid = (lx + rx) / 2;
            ls = new SegTree(lx, mid);
            rs = new SegTree(mid, rx);
            val = min(ls->val, rs->val);
            if(val == ls->val) id = ls->id;
            if(val == rs->val) id = rs->id;
        }
        else {
            val = mini[lx];
            id = lx;
        }
    }
    pair<int, int> getMin(int l, int r) {
        if(l <= lx && rx <= r) return {val, id};
        if(r <= lx || rx <= l) return {1e9, -1};
        return min(ls->getMin(l, r), rs->getMin(l, r));
    }
};

vector<int> v;

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    int n, q;
    cin >> n >> q;
    int g = 1;
    while(g <= 2*n) g *= 2;
    p.resize(n+1);
    mo.resize(n);
    mini.resize(g, 1e9);
    for(int i = 0; i < n; i++) {
        cin >> p[i].first >> p[i].second;
        s.insert(p[i].first);
        s.insert(p[i].second);
    }
    for(int y : s) {
        idx[y] = idx.size();
    }
    for(int i = 0; i < n; i++) {
        p[i].first = idx[p[i].first];
        p[i].second = idx[p[i].second];
        int x, y;
        tie(x, y) = p[i];
        mini[y] = min(mini[y], x);
        toEvent[p[i]] = i;
    }
    for(int i = 0; i < n; i++) {
        mo[i] = toEvent[p[i]];
    }
    pair<int, int> badP = {1e9, -1};
    p[n] = badP;
    toEvent[badP] = n;
    SegTree st(0, g);
    for(int i = 0; i < n; i++) {
        point[i][0] = toEvent[st.getMin(p[i].first, p[i].second + 1)];
        if(point[i][0] == i) point[i][0] = n;
    }
    for(int i = 0; i < 20; i++) {
        point[n][i] = n;
    }
    for(int i = 1; i < 20; i++) {
        for(int j = 0; j < n; j++) {
            point[j][i] = point[point[j][i-1]][i-1];
        }
    }
    while(q--) {
        int x, y;
        cin >> x >> y;
        x--; y--;
        if(x == y) {
            cout << "0\n";
            continue;
        }
        else if(p[x] == p[y]) {
            cout << "1\n";
            continue;
        }
        x = mo[x]; y = mo[y];
        int l = -1, r = n;
        while(l != r - 1) {
            int mid = (l + r + 1) / 2;
            int y2 = getPoint(y, mid);
            if(y2 == n) r = mid;
            else if(p[y2].first <= p[x].second) r = mid;
            else l = mid;
        }
        int y2 = getPoint(y, r);
        if(y2 == n || r == n) {
            cout << "impossible\n";
        }
        else if(!(p[y2].first <= p[x].second && p[x].second <= p[y2].second)) {
            cout << "impossible\n";
        }
        else {
            cout << r+1 << '\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