Submission #949621

#	Time	Username	Problem	Language	Result	Execution time	Memory
949621		sysia	Event Hopping (BOI22_events)	C++17	30 / 100	392 ms	46792 KiB

events

//Sylwia Sapkowska
#include <bits/stdc++.h>
#pragma GCC optimize("O3", "unroll-loops")
using namespace std;

void __print(int x) {cerr << x;}
void __print(long long x) {cerr << x;}
void __print(long double x) {cerr << x;}
void __print(char x) {cerr << "'" << x << "'";}
void __print(const char *x) {cerr << '"' << x << '"';}
void __print(const string &x) {cerr << '"' << x << '"';}
void __print(bool x) {cerr << (x ? "true" : "false");}

template<typename T, typename V>
void __print(const pair<T, V> &x) {cerr << '{'; __print(x.first); cerr << ", "; __print(x.second); cerr << '}';}
template<typename T>
void __print(const T &x) {int f = 0; cerr << '{'; for (auto &i: x) cerr << (f++ ? ", " : ""), __print(i); cerr << "}";}
void _print() {cerr << "]\n";}
template <typename T, typename... V>
void _print(T t, V... v) {__print(t); if (sizeof...(v)) cerr << ", "; _print(v...);}
#ifdef LOCAL
#define debug(x...) cerr << "[" << #x << "] = ["; _print(x)
#else
#define debug(x...)
#endif

#define int long long
typedef pair<int, int> T;
const int oo = 1e18, oo2 = 1e9+7, K = 20;
const int mod = 998244353;

void solve(){
    int n, q; cin >> n >> q;
    vector<T>a(n);
    vector<int>s;
    for (auto &[l, r]: a){
        cin >> l >> r;
        s.emplace_back(l);
        s.emplace_back(r);
    }
    sort(s.begin(), s.end());
    s.erase(unique(s.begin(), s.end()), s.end());
    auto get = [&](int x){ return (int)(lower_bound(s.begin(), s.end(), x)-s.begin());};
    for (auto &[l, r]: a){
        l = get(l); r = get(r);
        debug(l, r);
    }
    int m = (int)s.size();
   
    vector<vector<int>>L(m), R(m);
    for (int i = 0; i<n; i++){
        auto [l, r] = a[i];
        L[l].emplace_back(i);
        R[r].emplace_back(i);
    }
    set<T>secik; //r, i
    vector up(n+1, vector<int>(K));
    for (int rep = 0; rep<m; rep++){
        for (auto i: L[rep]){
            secik.insert({a[i].second, i});
        }
        for (auto i: R[rep]){
            secik.erase({rep, i});
            if (!secik.empty()) up[i][0] = secik.rbegin()->second;
            else up[i][0] = i;
            debug(i, up[i][0]);
            secik.insert({rep, i});
        }
        for (auto i: R[rep]){
            secik.erase({rep, i});
        }
    }
    for (int j = 1; j<K; j++){
        for (int i = 0; i<n;i++){
            up[i][j] = up[up[i][j-1]][j-1];
        }
    }
    while (q--){
        int l, r; cin >> l >> r;
        --l;--r;
        int ans = oo;
        int ll = 0, rr = n;
        while (rr >= ll){
            int mid = (ll+rr)/2;
            int curr = l;
            for (int i = K-1; i>=0; i--){
                // debug(i, l, up[l][i]);
                if (mid&(1<<i)){
                    curr = up[curr][i];
                }
            }
            if (a[curr].second > a[r].second){
                rr = mid-1;
            } else if (a[curr].second >= a[r].first){
                ans = mid;
                rr = mid-1;
            } else {
                ll = mid+1;
            }
        }
        if (ans == oo) {
            cout << "impossible\n";
            continue;
        }
        for (int i = K-1; i>=0; i--){
            if (ans&(1<<i)){
                l = up[l][i];
            }
        }
        debug(ans);
        if (a[l].second < a[r].first || a[l].second > a[r].second){
            cout << "impossible\n";
            continue;
        }
        if (l != r) ans++;
        cout << ans << "\n";
    }
}

int32_t main(){
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);

    int t = 1;
    //cin >> t;
    while (t--) solve();

    return 0;
}

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