Submission #1085329

#	Time	Username	Problem	Language	Result	Execution time	Memory
1085329		djs100201	Event Hopping (BOI22_events)	C++17	30 / 100	215 ms	32140 KiB

events

#include <bits/stdc++.h>
#define all(v) v.begin(), v.end()
using namespace std;
using ll = long long;
using P = pair<ll, ll>;
using PP = pair<ll, P>;
const ll n_ = 1e5 + 10, inf = (ll)2e9 * (ll)1e9 + 7, mod = 998244353;
ll n, m, tc = 1, a, b, c, d, sum, x, y, z, base, ans, k;
ll S[n_], E[n_], par[n_][20], rev[n_];
bool cmp(ll x, ll y) {
    if (E[x] ^ E[y]) return E[x] < E[y];
    return S[x] < S[y];
}
class seg {
   public:
    vector<ll> tree;
    ll base;
    seg(int n) {
        for (base = 1; base <= n; base *= 2);
        // 0~n쓰겠다
        tree.resize(n * 4 + 4);
        for (int i = 0; i < tree.size(); i++) tree[i] = -inf;
    }
    ll f(ll l, ll r) {
        l += base, r += base;
        ll ret = -inf;
        while (l <= r) {
            if (l % 2) ret = max(ret, tree[l++]);
            if (!(r % 2)) ret = max(ret, tree[r--]);
            l /= 2, r /= 2;
        }
        return ret;
    }
    void update(ll i, ll v) {
        i += base;
        tree[i] = max(tree[i], v);
        i /= 2;
        while (i) {
            tree[i] = max(tree[i * 2], tree[i * 2 + 1]);
            i /= 2;
        }
    }
};
void solve() {
    ll Q;
    cin >> n >> Q;
    vector<ll> T, idx;
    for (int i = 1; i <= n; i++) {
        cin >> S[i] >> E[i];
        T.push_back(S[i]), T.push_back(E[i]);
        idx.push_back(i);
    }
    sort(all(idx), cmp), sort(all(T)), T.erase(unique(all(T)), T.end());
    seg ST(2 * n + 1);
    for (int i = 0; i < n; i++) {
        rev[idx[i]] = i;
        // cout<<idx[i]<<' '<<i<<endl;
        ll a = lower_bound(all(T), S[idx[i]]) - T.begin();
        ST.update(a, i);
    }
    for (int i = 0; i < n; i++) {
        ll l = lower_bound(all(T), S[idx[i]]) - T.begin(), r = lower_bound(all(T), E[idx[i]]) - T.begin();
        par[i][0] = ST.f(0, r);
    }
    for (int j = 1; j < 20; j++) {
        for (int i = 0; i < n; i++) {
            par[i][j] = par[par[i][j - 1]][j - 1];
        }
    }
    while (Q--) {
        cin >> x >> y;
        if (x == y) {
            cout << "0" << '\n';
            continue;
        }
        x = rev[x], y = rev[y];
        ll l = 0, r = n;
        ans = inf;
        while (l <= r) {
            ll mid = (l + r) / 2, now = x, cost = mid;
            for (int i = 19; i >= 0; i--) {
                if (cost >= (1ll << i)) {
                    cost -= (1ll << i);
                    now = par[now][i];
                }
            }
            if (E[idx[now]] >= S[idx[y]]) {
                ans = min(ans, mid);
                r = mid - 1;
            } else
                l = mid + 1;
        }
        ll now = x, cost = ans;
        for (int i = 19; i >= 0; i--) {
            if (cost >= (1ll << i)) {
                cost -= (1ll << i);
                now = par[now][i];
            }
        }
        assert(now != y);
        if (E[idx[now]] < S[idx[y]] || E[idx[now]] > E[idx[y]])
            cout << "impossible" << '\n';
        else
            cout << ans + 1 << '\n';
    }
}
 
int main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0), cout.tie(0);
    // cin >> tc;
    while (tc--) solve();
};

Compilation message (stderr)

events.cpp: In constructor 'seg::seg(int)':
events.cpp:22:27: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   22 |         for (int i = 0; i < tree.size(); i++) tree[i] = -inf;
      |                         ~~^~~~~~~~~~~~~
events.cpp: In function 'void solve()':
events.cpp:62:12: warning: unused variable 'l' [-Wunused-variable]
   62 |         ll l = lower_bound(all(T), S[idx[i]]) - T.begin(), r = lower_bound(all(T), E[idx[i]]) - T.begin();
      |            ^

• Subtask 1: 10 / 10
• Subtask 2: 0 / 10
• Subtask 3: 0 / 15
• Subtask 4: 0 / 15
• Subtask 5: 20 / 20
• Subtask 6: 0 / 30