Submission #595620

#	Time	Username	Problem	Language	Result	Execution time	Memory
595620		definitelynotmee	Event Hopping (BOI22_events)	C++98	30 / 100	118 ms	11332 KiB

events

#include<bits/stdc++.h>
#define ff first
#define ss second
#define all(x) x.begin(), x.end()
using namespace std;
using ll = long long;
using pii = pair<int,int>;
using pll = pair<ll,ll>;
template<typename T>
using matrix = vector<vector<T>>;
const int INF = 1<<30;

int main() {
    cin.tie(0)->sync_with_stdio(0);

    int n, q;
    cin >> n >> q;
    vector<pii> v(n);
    for(pii& i : v){
        cin >> i.ff >> i.ss;
        i.ff = INF-i.ff;
        i.ss = INF-i.ss;
        swap(i.ff,i.ss);
    }
    // cout << "----------\n";
    // for(pii i : v)
    //     cout << i.ff << ' ' << i.ss << '\n';
    // cout << "----------\n";
    vector<int>o(n);
    iota(all(o),0);
    sort(all(o),[&](int a, int b){
        return v[a] > v[b];
    });

    vector<int> jmp(n);
    vector<int> st;

    for(int i : o){
        int ini = 0, fim = st.size();
        while(ini!=fim){
            int m = (ini+fim)>>1;
            if(v[st[m]].ff <= v[i].ss)
                fim = m;
            else ini = m+1;
        }
        if(ini == st.size()){
            jmp[i] = i;
        } else jmp[i] = st[ini];
        
        while(!st.empty() && v[st.back()].ss <= v[i].ss)
            st.pop_back();
        if(st.empty() || v[st.back()].ff > v[i].ff)
            st.push_back(i);
        // cout << i << ":\n";
        // for(int i : st)
        //     cout << i << ' ';
        // cout << '\n';
    }

    matrix<int> lift(20,vector<int>(n));
    for(int i = 0; i < n; i++){
        lift[0][i] = jmp[i]; 
        // cout << jmp[i] << ' ';
    }
    // cout << '\n';
    for(int i = 1; i < 20; i++){
        for(int j = 0; j < n; j++){
            lift[i][j] = lift[i-1][lift[i-1][j]];
        }
    }
    
    while(q--){
        int a, b;
        cin >> a >> b;
        a--, b--;
        swap(a,b);
        if(v[a] > v[b]){
            cout << "impossible\n";
            continue;
        }
        if(a == b){
            cout << 0 << '\n';
            continue;
        }
        if(v[a].ss >= v[b].ff){
            cout << 1 << '\n';
            continue;
        }
        int ct = 2;
        for(int i = 19; i >= 0; i--){
            if(v[lift[i][a]].ss < v[b].ff)
                ct+=1<<i, a = lift[i][a];
        }
        a = lift[0][a];
        if(v[a].ss >= v[b].ff){
            cout << ct << '\n';
        } else {
            cout << "impossible\n";
        }
    }

}

Compilation message (stderr)

events.cpp: In function 'int main()':
events.cpp:46:16: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   46 |         if(ini == st.size()){
      |            ~~~~^~~~~~~~~~~~

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