Submission #1176992

#	Time	Username	Problem	Language	Result	Execution time	Memory
1176992		trinm01	Event Hopping (BOI22_events)	C++20	100 / 100	332 ms	74124 KiB

events

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

#define int long long
#define FOR(i, l, r) for (int i = (l); i <= (r); i++)

const int mod = 998244353;
const int MAXN = 5 * 1e5 + 5;
const int oo = 1e18;

struct pii
{
    int fi, se, u;
};

int n, q, m;
int par[MAXN], up[MAXN][25], cost[MAXN][25];
pii a[MAXN], b[MAXN];
pii st[4 * MAXN];
bool cmp(pii a, pii b)
{
    return a.fi < b.fi;
}

void nen()
{
    set<int> s;
    unordered_map<int, int> mp;
    FOR(i, 1, n)
    {
        s.insert(a[i].fi);
        s.insert(a[i].se);
    }
    int cnt = 1;
    for (auto x : s)
    {
        mp[x] = cnt++;
    }
    m = cnt;
    FOR(i, 1, n)
    {
        a[i].fi = mp[a[i].fi];
        a[i].se = mp[a[i].se];
    }
}
void seg_init(int id, int l, int r)
{
    if (l == r)
    {
        st[id] = {oo, 0, oo};
        return;
    }
    int mid = (l + r) / 2;
    seg_init(id * 2, l, mid);
    seg_init(id * 2 + 1, mid + 1, r);
    st[id] = st[id * 2];
    if (st[id * 2 + 1].fi < st[id].fi)
        st[id] = st[id * 2 + 1];
}

void update(int id, int l, int r, int pos, int val, int idx)
{
    if (pos < l || pos > r)
        return;
    if (l == r)
    {
        if (val < st[id].fi)
            st[id] = {val, idx, 0};
        return;
    }
    int mid = (l + r) / 2;
    if (pos <= mid)
        update(id * 2, l, mid, pos, val, idx);
    else
        update(id * 2 + 1, mid + 1, r, pos, val, idx);
    st[id] = st[id * 2];
    if (st[id * 2 + 1].fi < st[id].fi)
        st[id] = st[id * 2 + 1];
}
pii get(int id, int l, int r, int ql, int qr)
{
    if (ql > r || qr < l)
        return {oo, 0, oo};
    if (ql <= l && r <= qr)
        return st[id];
    int mid = (l + r) / 2;
    pii left = get(id * 2, l, mid, ql, qr);
    pii right = get(id * 2 + 1, mid + 1, r, ql, qr);
    return (left.fi < right.fi ? left : right);
}

signed main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);

    cin >> n >> q;
    FOR(i, 1, n)
    {
        cin >> a[i].fi >> a[i].se;
        a[i].u = i;
        b[i] = a[i];
    }

    nen();

    seg_init(1, 1, m);

    sort(a + 1, a + n + 1, cmp);
    FOR(i, 1, n)
    {
        int u = a[i].u;
        pii t = get(1, 1, m, a[i].fi, a[i].se);
        par[u] = t.se;
        update(1, 1, m, a[i].se, a[i].fi, u);
    }

    FOR(i, 1, n)
    {
        if (par[i] == 0)
            par[i] = i;
        // cout << par[i] << ' ';
        up[i][0] = par[i];
        cost[i][0] = (par[i] != i ? 1 : 0);
    }
    // cout << "\n";
    for (int k = 1; k < 21; k++)
    {
        FOR(u, 1, n)
        {
            up[u][k] = up[up[u][k - 1]][k - 1];
            cost[u][k] = cost[u][k - 1] + cost[up[u][k - 1]][k - 1];
        }
    }

    // cout << get(1, 1, m, 7, 9).fi;
    while (q--)
    {
        int u, v;
        cin >> u >> v;
        if (u == v)
        {
            cout << 0 << "\n";
            continue;
        }
        if (b[u].se > b[v].se)
        {
            cout << "impossible" << "\n";
            continue;
        }
        int sum = 0;
        bool possible = true;
        int cur = v;
        for (int k = 19; k >= 0; k--)
        {
            if (b[up[cur][k]].fi > b[u].se)
            {
                sum += cost[cur][k];
                cur = up[cur][k];
            }
        }
        // if (!possible)
        // {
        //     cout << "impossible" << "\n";
        //     continue;
        // }
        sum++;
        if (b[u].se >= b[cur].fi && b[u].se <= b[cur].se)
        {
            cout << sum << "\n";
            continue;
        }
        cur = up[cur][0];
        if (b[u].se >= b[cur].fi && b[u].se <= b[cur].se)
        {
            cout << sum + 1 << "\n";
            continue;
        }
        cur = up[cur][0];
        if (b[u].se >= b[cur].fi && b[u].se <= b[cur].se)
        {
            cout << sum + 2 << "\n";
            continue;
        }
        cout << "impossible" << "\n";
    }

    return 0;
}

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