Submission #1204074

#	Time	Username	Problem	Language	Result	Execution time	Memory
1204074		CrabCNH	Event Hopping (BOI22_events)	C++20	100 / 100	220 ms	48640 KiB

events

#include <bits/stdc++.h>

#define task   "BriantheCrab"

#define int    long long
#define pii    pair <int, int>
#define fi     first
#define se     second
#define szf    sizeof
#define sz(s)  (int)((s).size())

using namespace std;

template <class T> void mini (T &t, T f) {if (t > f) t = f;}
template <class T> void maxi (T &t, T f) {if (t < f) t = f;}

const int maxN = 1e5 + 5;
const int inf = 1e18 + 7;
const int LOG = 20;
const int mod = 1e9 + 7;

int n, q;
pii a[maxN];
int up[maxN][LOG], cost[maxN][LOG];

struct ST {
    struct Node {
        int l, pos;
        bool operator < (const Node &other) const {
            return l < other.l;
        }
    };
    
    vector <Node> st;
    
    void init (int n) {
        st.resize (n << 2, {inf, inf});
    }
    
    void upd (int id, int l, int r, int pos, int val, int curSeg) {
        if (pos < l || pos > r) {
            return;
        }
        if (l == r) {
            st[id] = min (st[id], {val, curSeg});
            return;
        }
        int mid = (l + r) >> 1;
        upd (id * 2, l, mid, pos, val, curSeg);
        upd (id * 2 + 1, mid + 1, r, pos, val, curSeg);
        st[id] = min (st[id * 2], st[id * 2 + 1]);
    }
    
    Node get (int id, int l, int r, int u, int v) {
        if (u > r || v < l) {
            return {inf, inf};
        }
        if (u <= l && r <= v) {
            return st[id];
        }
        int mid = (l + r) >> 1;
        auto tL = get (id * 2, l, mid, u, v);
        auto tR = get (id * 2 + 1, mid + 1, r, u, v);
        return min (tL, tR);
    }
};

ST T;

void solve () {
    cin >> n >> q;
    vector <int> zip;
    for (int i = 1; i <= n; i ++) {
        cin >> a[i].fi >> a[i].se;
        zip.push_back (a[i].fi);
        zip.push_back (a[i].se);
    }
    sort (zip.begin (), zip.end ());
    zip.erase (unique (zip.begin (), zip.end ()), zip.end ());
    int lim = zip.size ();
    T.init (lim);
    for (int i = 1; i <= n; i ++) {
        a[i].fi = lower_bound (zip.begin (), zip.end (), a[i].fi) - zip.begin () + 1;
        a[i].se = lower_bound (zip.begin (), zip.end (), a[i].se) - zip.begin () + 1;
        T.upd (1, 1, lim, a[i].se, a[i].fi, i);
    }
    for (int i = 1; i <= n; i ++) {
        auto [bestL, bestid] = T.get (1, 1, lim, a[i].fi, a[i].se);
        up[i][0] = ((bestL == a[i].fi) ? i : bestid);
        //cout << bestL << ' ' << bestid << '\n';
        cost[i][0] = ((bestL == a[i].fi) ? 0 : 1);
    }
    for (int j = 1; j < LOG; j ++) {
        for (int i = 1; i <= n; i ++) {
            up[i][j] = up[up[i][j - 1]][j - 1];
            cost[i][j] = cost[up[i][j - 1]][j - 1] + cost[i][j - 1];
        }
    }
    while (q --) {
        int s, t;
        cin >> s >> t;
        if (s == t) {
            cout << "0\n";
            continue;
        }
        if (a[s].fi >= a[t].se) {
            cout << "impossible\n";
            continue;
        }
        int res = 0;
        for (int j = LOG - 1; j >= 0; j --) {
            if (a[up[t][j]].fi > a[s].se) {
                res += cost[t][j];
                t = up[t][j];
            }
        }
        int flg = 1;
        for (int i = 1; i <= 3; i ++) {
            if (a[s].se >= a[t].fi && a[s].se <= a[t].se) {
                cout << res + i << '\n';
                flg = 0;
                break;
            }
            t = up[t][0];
        }
        if (flg) {
            cout << "impossible\n";
        }
    }
}

signed main () {
    cin.tie (nullptr) -> sync_with_stdio (false);
    if (fopen (task".inp", "r")) {
        freopen (task".inp", "r", stdin);
        freopen (task".out", "w", stdout);
    }
    int t = 1;
    //cin >> t;
    while (t --) {
        solve ();
    } 
    return 0;
}
// thfdgb

Compilation message (stderr)

events.cpp: In function 'int main()':
events.cpp:135:17: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  135 |         freopen (task".inp", "r", stdin);
      |         ~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
events.cpp:136:17: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  136 |         freopen (task".out", "w", stdout);
      |         ~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

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