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Submission #1000459

# Submission time Handle Problem Language Result Execution time Memory
1000459 2024-06-17T14:23:35 Z anango Event Hopping (BOI22_events) C++17
0 / 100
 297 ms 42392 KB 
#include <bits/stdc++.h>
#define int long long
using namespace std;


signed main() {
    #ifndef ONLINE_JUDGE
        // for getting input from input.txt
        //freopen("input.txt", "r", stdin);
        // for writing output to output.txt
        //freopen("output.txt", "w", stdout);
    #endif
    /*#ifdef ONLINE_JUDGE
    	ios_base::sync_with_stdio(false);
    	cin.tie(NULL);
    #endif*/ //fast IO
    ios_base::sync_with_stdio(false);
    	cin.tie(NULL);
    //for each time t, compute latest[t] = latest time you can get to with at most 1 switch starting at t
    //then binary lifting
    int n,q;
    cin >> n >> q;
    vector<pair<int,int>> events;
    vector<vector<int>> sweep;
    vector<int> coords;
    map<int,int> revcoords;
    for (int i=0; i<n; i++) {
        int st,en;
        cin >> st >> en;
        events.push_back({st,en});
        coords.push_back(st);
        coords.push_back(en);
    }
    sort(coords.begin(), coords.end());
    coords.erase(unique(coords.begin(), coords.end()),coords.end());
    
    int k = coords.size();
    for (int i=0; i<k; i++) {
        revcoords[coords[i]] = i;
    }
    
    for (int i=0; i<events.size(); i++) {
        int st,en;
        st=events[i].first;
        en=events[i].second;
        sweep.push_back({revcoords[st],-1,i});
        sweep.push_back({revcoords[en],1,i});
        events[i] = {revcoords[st],revcoords[en]};
    }
    sort(sweep.begin(), sweep.end());
    set<int> indices;
    multiset<int> endings;
    vector<int> latest(k,-1);
    
    for (auto ev:sweep) {
        int a,b,ind;
        a=ev[0];
        b=ev[1];
        ind=ev[2];
        if (b==-1) {
            indices.insert(ind);
            endings.insert(events[ind].second);
        }
        else {
            indices.erase(ind);
            endings.erase(endings.find(events[ind].second));
        }
        if (endings.size()) {
            latest[a] = *endings.rbegin();
        }
        else {
            latest[a] = a;
        }
    }
    int maxlift=20;
    vector<vector<int>> lift(k,vector<int>(maxlift+1,-1));
    for (int i=0; i<k; i++) {
        lift[i][0] = latest[i];
        //cout << i <<" " << latest[i] << endl;
    }
    for (int p=0; p<maxlift; p++) {
        for (int i=0; i<k; i++) {
            lift[i][p+1] = lift[lift[i][p]][p];
            //cout << i <<" " << p+1 <<" " << lift[i][p+1] << endl;
        }
    }

    for (int i=0; i<q; i++) {
        int x,y;
        cin >> x >> y;
        x--;
        y--;
        int answer = 0;
        int startstart = events[x].first;
        int start = events[x].second;
        int endstart = events[y].first;
        int end = events[y].second;
        if (x==y || (startstart<=endstart && endstart<=start)) {
            cout << 0 << endl;
            continue;
        }
        if (endstart <= start && start<=end) {
            cout << 1 << endl;
            continue;
        }
        int cur = start;
        for (int p=maxlift; p>=0; p--) {
            int ncur = lift[cur][p];
            //cout << p <<" " << cur <<" " << ncur << endl;
            if (ncur<endstart) {
                cur=ncur;
                answer+=1LL<<p;
            }
        }
        cur=lift[cur][0];
        //cout << "DOING " << start << " " << end << " " << cur << endl;

        if (!(endstart<=cur && cur<=end)) {
            cout << "impossible" << endl;
        }
        else {
            cout << answer+2 << endl;
        }
    }

}

Compilation message

events.cpp: In function 'int main()':
events.cpp:42:20: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<std::pair<long long int, long long int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   42 |     for (int i=0; i<events.size(); i++) {
      |                   ~^~~~~~~~~~~~~~

Subtask #1
0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 1 ms 344 KB Output is correct
2 Correct 286 ms 41876 KB Output is correct
3 Correct 297 ms 42112 KB Output is correct
4 Incorrect 288 ms 41636 KB Output isn't correct
5 Halted 0 ms 0 KB -

Subtask #2
0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 0 ms 348 KB Output is correct
2 Correct 0 ms 348 KB Output is correct
3 Correct 1 ms 860 KB Output is correct
4 Incorrect 1 ms 856 KB Output isn't correct
5 Halted 0 ms 0 KB -

Subtask #3
0 / 15.0

# Verdict Execution time Memory Grader output
1 Correct 0 ms 348 KB Output is correct
2 Correct 0 ms 348 KB Output is correct
3 Correct 1 ms 860 KB Output is correct
4 Incorrect 1 ms 856 KB Output isn't correct
5 Halted 0 ms 0 KB -

Subtask #4
0 / 15.0

# Verdict Execution time Memory Grader output
1 Correct 0 ms 348 KB Output is correct
2 Correct 0 ms 348 KB Output is correct
3 Correct 1 ms 860 KB Output is correct
4 Incorrect 1 ms 856 KB Output isn't correct
5 Halted 0 ms 0 KB -

Subtask #5
0 / 20.0

# Verdict Execution time Memory Grader output
1 Correct 283 ms 41796 KB Output is correct
2 Correct 290 ms 42392 KB Output is correct
3 Incorrect 287 ms 41640 KB Output isn't correct
4 Halted 0 ms 0 KB -

Subtask #6
0 / 30.0

# Verdict Execution time Memory Grader output
1 Correct 1 ms 344 KB Output is correct
2 Correct 286 ms 41876 KB Output is correct
3 Correct 297 ms 42112 KB Output is correct
4 Incorrect 288 ms 41636 KB Output isn't correct
5 Halted 0 ms 0 KB -