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Submission #599907

# Submission time Handle Problem Language Result Execution time Memory
599907 2022-07-20T07:38:28 Z isaachew Event Hopping (BOI22_events) C++17
40 / 100
 1500 ms 3780 KB 
#include <bits/stdc++.h>
/*
 The whole event space is a DAG
 
 Calculate the minimum switching to get from time A to B
 
 Get from an event to another
 
 Event to event
 Every event is either completely contained in another, or not
 Completely contained = directed edge from contained
 Not = earlier end to later end
 An O(E) = O(N^2) should get 35 points
 Use RQTree to get minimum switches by sorting by end time; O(NQ log N)
 You cannot switch to an event with same end time; waste
 ST5: Earlier start time = earlier end time (start time is increasing)
 Go backwards and use segment tree
 
 ST4: O(NQ), not O(NQ log N)
 
 Go backwards; min switches from is increasing
 You now have to go from a time to an event
 Switches can be calculated by using min number of switches for every time
 
 If the start (end) event was not a key event, add 1
 
 Edges split and join; an event inside another is just a join
 Select a chain of events with minimum switches
 
 If there was a chain that connected two events, it would have to be part of the main chain
 
 1         2        3           4  5  6 7
        \                            /
      S  1            2             3E
 1         2          3             4 5 6
 
 Update a chain?
 If the start is moved forward, the chain stays
 If the end is moved backward, the chain ?
 If start is moved backwards, extend the chain
 */

int n,q;
std::vector<int> rqtree;
std::vector<int> endpoints;
int query(int l,int r,int nl=0,int nr=n+1,int ni=0){
    //std::cout<<nl<<"/"<<nr<<'\n';
    if(nl+1>=nr){
        if(l<=endpoints[nl]&&r>endpoints[nl])return rqtree[ni];
        return 1000000001;
    }
    if(l>=endpoints[nr]||r<=endpoints[nl])return 1000000001;
    if(l<=endpoints[nl]&&r>=endpoints[nr]){
        return rqtree[ni];
    }
    int nm=(nl+nr)/2;
    return std::min(query(l,r,nl,nm,ni+1),query(l,r,nm,nr,ni+2*(nm-nl)));
}
void update(int loc,int val,int nl=0,int nr=n+1,int ni=0){
    //std::cout<<"upd "<<nl<<' '<<nr<<'\n';
    if(nl+1>=nr){
        if(loc==endpoints[nl])rqtree[ni]=std::min(rqtree[ni],val);
        return;
    }
    int nm=(nl+nr)/2;
    if(loc<endpoints[nm]){
        rqtree[ni]=std::min(rqtree[ni],val);
        update(loc,val,nl,nm,ni+1);
    }else{
        rqtree[ni]=std::min(rqtree[ni],val);
        update(loc,val,nm,nr,ni+2*(nm-nl));
    }
}
std::vector<std::pair<int,int>> events;
std::vector<std::pair<int,int>> queries;
std::vector<int> s_events;
std::vector<int> i_s_events;
std::vector<int> out_arr;
int main(){
    std::cin>>n>>q;
    for(int i=0;i<n;i++){
        int a,b;
        std::cin>>a>>b;
        events.push_back({a,b});
        endpoints.push_back(b);
        s_events.push_back(i);
    }
    
    endpoints.push_back(0);
    endpoints.push_back(1000000001);
    std::sort(endpoints.begin(),endpoints.end());
      
    std::sort(s_events.begin(),s_events.end(),[](int a,int b){return events[a].second==events[b].second?events[a].first<events[b].first:events[a].second<events[b].second;});
    i_s_events.resize(n,-1);
    for(int i=0;i<n;i++){
        i_s_events[s_events[i]]=i;
    }
    for(int i=0;i<q;i++){
        int start,end;
        std::cin>>start>>end;
        start--,end--;
        int cswc=0;//count
        int cset=1000000001;//end time
        int nset=1000000001;//next end time (first start)
        cset=nset=events[end].first;
        int f_index=std::upper_bound(endpoints.begin(),endpoints.end(),events[end].second)-endpoints.begin()-2;
        int s_index=i_s_events[start];
        //std::cout<<s_index<<" to "<<f_index<<'\n';
        //std::cout<<events[end].second<<"?\n";
        if(events[end].second<events[start].second){
            cswc=-1;
        }
        if(start==end){
            std::cout<<"0\n";
            continue;
        }
        for(int p=f_index;p>=s_index;p--){
            //if(p==i_s_events[end])continue;
            int ceid=s_events[p];
            //std::cout<<ceid<<";\n";
            if(events[ceid].second<nset){
                cswc=-1;
                break;
            }else if(events[ceid].second<cset){
                //std::cout<<"inc\n";
                cswc++;
                cset=nset;
            }else{
                
            }
            nset=std::min(nset,events[ceid].first);
        }
        if(cswc==-1){
            std::cout<<"impossible\n";
        }else{
            std::cout<<cswc+1<<'\n';
        }
    }
}

Subtask #1
0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 0 ms 212 KB Output is correct
2 Execution timed out 1583 ms 2900 KB Time limit exceeded
3 Halted 0 ms 0 KB -

Subtask #2
10.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 1 ms 212 KB Output is correct
2 Correct 0 ms 212 KB Output is correct
3 Correct 2 ms 212 KB Output is correct
4 Correct 2 ms 212 KB Output is correct
5 Correct 1 ms 212 KB Output is correct
6 Correct 1 ms 212 KB Output is correct
7 Correct 2 ms 212 KB Output is correct
8 Correct 1 ms 212 KB Output is correct
9 Correct 1 ms 212 KB Output is correct

Subtask #3
15.0 / 15.0

# Verdict Execution time Memory Grader output
1 Correct 1 ms 212 KB Output is correct
2 Correct 0 ms 212 KB Output is correct
3 Correct 2 ms 212 KB Output is correct
4 Correct 2 ms 212 KB Output is correct
5 Correct 1 ms 212 KB Output is correct
6 Correct 1 ms 212 KB Output is correct
7 Correct 2 ms 212 KB Output is correct
8 Correct 1 ms 212 KB Output is correct
9 Correct 1 ms 212 KB Output is correct
10 Correct 0 ms 212 KB Output is correct
11 Correct 0 ms 212 KB Output is correct
12 Correct 2 ms 212 KB Output is correct
13 Correct 2 ms 212 KB Output is correct
14 Correct 1 ms 212 KB Output is correct
15 Correct 2 ms 212 KB Output is correct
16 Correct 1 ms 212 KB Output is correct
17 Correct 2 ms 212 KB Output is correct
18 Correct 1 ms 212 KB Output is correct
19 Correct 797 ms 936 KB Output is correct
20 Correct 890 ms 968 KB Output is correct
21 Correct 320 ms 1252 KB Output is correct
22 Correct 260 ms 1384 KB Output is correct
23 Correct 318 ms 1728 KB Output is correct
24 Correct 287 ms 1708 KB Output is correct
25 Correct 944 ms 1388 KB Output is correct

Subtask #4
15.0 / 15.0

# Verdict Execution time Memory Grader output
1 Correct 1 ms 212 KB Output is correct
2 Correct 0 ms 212 KB Output is correct
3 Correct 2 ms 212 KB Output is correct
4 Correct 2 ms 212 KB Output is correct
5 Correct 1 ms 212 KB Output is correct
6 Correct 1 ms 212 KB Output is correct
7 Correct 2 ms 212 KB Output is correct
8 Correct 1 ms 212 KB Output is correct
9 Correct 1 ms 212 KB Output is correct
10 Correct 0 ms 212 KB Output is correct
11 Correct 0 ms 212 KB Output is correct
12 Correct 2 ms 212 KB Output is correct
13 Correct 2 ms 212 KB Output is correct
14 Correct 1 ms 292 KB Output is correct
15 Correct 1 ms 212 KB Output is correct
16 Correct 1 ms 212 KB Output is correct
17 Correct 2 ms 212 KB Output is correct
18 Correct 1 ms 212 KB Output is correct
19 Correct 109 ms 2672 KB Output is correct
20 Correct 87 ms 2752 KB Output is correct
21 Correct 102 ms 2716 KB Output is correct
22 Correct 91 ms 2648 KB Output is correct
23 Correct 103 ms 3440 KB Output is correct
24 Correct 110 ms 3780 KB Output is correct
25 Correct 88 ms 3680 KB Output is correct

Subtask #5
0 / 20.0

# Verdict Execution time Memory Grader output
1 Execution timed out 1549 ms 2900 KB Time limit exceeded
2 Halted 0 ms 0 KB -

Subtask #6
0 / 30.0

# Verdict Execution time Memory Grader output
1 Correct 0 ms 212 KB Output is correct
2 Execution timed out 1583 ms 2900 KB Time limit exceeded
3 Halted 0 ms 0 KB -