Submission #949702

#	Time	Username	Problem	Language	Result	Execution time	Memory
949702		sysia	Event Hopping (BOI22_events)	C++17	100 / 100	482 ms	51236 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;

struct Tree{
    vector<T>tab;
    int size = 1;

    Tree(int n){
        while (size < n) size*=2;
        tab.assign(2*size, {oo, oo});
    }

    void update(int x, T v){
        x += size;
        tab[x] = min(tab[x], v);
        while (x){
            x/=2;
            tab[x] = min(tab[2*x], tab[2*x+1]);
        }
    }

    T query(int l, int r){
        T ans = {oo, oo};
        for (l += size-1, r += size+1; r-l>1; l/=2, r/=2) {
            if (!(l&1)) ans = min(ans, tab[l+1]);
            if (r&1) ans = min(ans, tab[r-1]);
        }
        return ans;
    }
};

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);
    }
    vector up(n+1, vector<int>(K));
    Tree t(m+1);
    for (int i = 0; i<n; i++) t.update(a[i].second, {a[i].first, i});
    //przedzial o minimalnym lewym koncu, z ktorego da sie doskoczyc na i-ty 
    for (int rep = 0; rep < m; rep++){
        for (auto i: L[rep]){
            auto [left, prev] = t.query(a[i].first, a[i].second);
            up[i][0] = (prev == oo ? i : prev);
            debug(i, up[i][0]);
        }
    }
    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;
        debug(l, r);
        int ans = 0;
        int ll = 0, rr = n;
        while (rr >= ll){
            int mid = (ll+rr)/2;
            int curr = r;
            for (int i = K-1; i>=0; i--){
                // debug(i, l, up[l][i]);
                if (mid&(1<<i)){
                    curr = up[curr][i];
                }
            }
            //umiem doskoczyc do a[curr]
            //czy z l da sie przeskoczyc na curr kiedys(?) --> a[curr].second >= a[l].second >= a[curr].first;
            if (a[curr].first > a[l].second) {
                ll = mid+1;
            } else {
                ans = mid;
                rr = mid-1;
            }
        }
        for (int i = K-1; i>=0; i--){
            if (ans&(1<<i)){
                r = up[r][i];
            }
        }
        debug(l, r);
        //czy z l da sie przeskoczyc na r
        if (a[r].first <= a[l].second && a[l].second <= a[r].second){
            cout << ans + (l!=r) << "\n";
        } else {
            cout << "impossible\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: 10 / 10
• Subtask 3: 15 / 15
• Subtask 4: 15 / 15
• Subtask 5: 20 / 20
• Subtask 6: 30 / 30