Submission #750603

#	Time	Username	Problem	Language	Result	Execution time	Memory
750603		stevancv	Event Hopping (BOI22_events)	C++14	100 / 100	249 ms	34268 KiB

events

#include <bits/stdc++.h>
#define ll long long
#define ld long double
#define sp ' '
#define en '\n'
#define smin(a, b) a = min(a, b)
#define smax(a, b) a = max(a, b)
using namespace std;
const int N = 1e5 + 2;
const int inf = 1e9;
int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    int n, q;
    cin >> n >> q;
    vector<int> l(n), r(n);
    for (int i = 0; i < n; i++) {
        cin >> l[i] >> r[i];
    }
    vector<int> order(n);
    iota(order.begin(), order.end(), 0);
    sort(order.begin(), order.end(), [&] (int i, int j) {
        if (r[i] != r[j]) return r[i] < r[j];
        return l[i] < l[j];
    });
    vector<int> gdesibreti(n);
    for (int i = 0; i < n; i++) gdesibreti[order[i]] = i;
    vector<int> tl(n), tr(n);
    for (int i = 0; i < n; i++) {
        tl[i] = l[order[i]];
        tr[i] = r[order[i]];
    }
    swap(l, tl); swap(r, tr);
    vector<vector<pair<int, int>>> rmq(n, vector<pair<int, int>>(17));
    for (int i = 0; i < n; i++) rmq[i][0] = {l[i], i};
    for (int j = 1; j < 17; j++) {
        for (int i = 0; i + (1 << j) <= n; i++) {
            rmq[i][j] = min(rmq[i][j - 1], rmq[i + (1 << (j - 1))][j - 1]);
        }
    }
    vector<int> logs(n + 1);
    int z = 0;
    for (int i = 1; i <= n; i++) {
        if (i == (1 << (z + 1))) z += 1;
        logs[i] = z;
    }
    auto Query = [&] (int l, int r) {
        int o = logs[r - l + 1];
        return min(rmq[l][o], rmq[r - (1 << o) + 1][o]);
    };
    vector<int> dokle(n, -1);
    for (int i = 0; i < n; i++) {
        int lo = 0, hi = i - 1, idx = i;
        while (lo <= hi) {
            int mid = lo + hi >> 1;
            if (l[i] <= r[mid]) {
                hi = mid - 1;
                idx = mid;
            }
            else lo = mid + 1;
        }
        dokle[i] = idx;
    }
    vector<vector<int>> lift(n, vector<int>(17));
    for (int i = 0; i < n; i++) lift[i][0] = dokle[i];
    for (int j = 1; j < 17; j++) {
        for (int i = 0; i < n; i++) {
            lift[i][j] = lift[Query(lift[i][j - 1], i).second][j - 1];
        }
    }
    while (q--) {
        int a, b;
        cin >> a >> b;
        a -= 1; b -= 1;
        a = gdesibreti[a]; b = gdesibreti[b];
        if (a == b) {
            cout << 0 << en;
            continue;
        }
        if (l[b] <= r[a] && r[a] <= r[b]) {
            cout << 1 << en;
            continue;
        }
        if (a > b) {
            cout << "impossible" << en;
            continue;
        }
        int ans = 0;
        for (int i = 16; i >= 0; i--) {
            if (a < lift[b][i]) {
                ans += (1 << i);
                b = Query(lift[b][i], b).second;
            }
        }
        if (a < lift[b][0]) cout << "impossible" << en;
        else cout << ans + 1 << en;
    }
    return 0;
}

Compilation message (stderr)

events.cpp: In function 'int main()':
events.cpp:56:26: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
   56 |             int mid = lo + hi >> 1;
      |                       ~~~^~~~

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