Submission #1080616

#	Time	Username	Problem	Language	Result	Execution time	Memory
1080616		isaachew	Sparklers (JOI17_sparklers)	C++17	0 / 100	1 ms	348 KiB

sparklers

#include <bits/stdc++.h>
/*
 The sparkler should move in both directions from the initial person after it is lit
 
 If two people meet, they should do so as soon as possible, otherwise it wouldn't make a difference
 
 A path actually depends on the sum of distances of the first and last people from the person with the sparkler
 
 */
int main(){
    std::ios::sync_with_stdio(0);
    std::cin.tie(0);
    long long n,k,t;
    std::cin>>n>>k>>t;
    k--;
    std::vector<int> places;
    for(int i=0;i<n;i++){
        int a;
        std::cin>>a;
        places.push_back(a);
    }
    
    long long lower=-1,upper=1e9;//min distance a sparkler can burn for
    while(lower+1<upper){
        long long mid=(lower+upper)/2;
        //std::cout<<mid<<'\n';
        std::vector<std::pair<long long,long long>> toleft,toright;//cost, profit
        long long curmin=0;
        long long cursum=0;
        for(int i=k-1;i>=0;i--){
            //std::cout<<i+1<<"?"<<i<<'\n';
            cursum-=(places[i+1]-places[i]);
            curmin=std::min(cursum,curmin);
            cursum+=mid;
            if(cursum>0){
                toleft.push_back({-curmin,cursum});
                cursum=0;curmin=0;
            }
        }
        std::pair<long long,long long> leftex={-curmin,-cursum};//cursum <= 0
        //std::cout<<"yes\n";
        curmin=0;cursum=0;
        for(int i=k;i<n-1;i++){
            //std::cout<<i+1<<"?"<<i<<'\n';
            cursum-=(places[i+1]-places[i]);
            curmin=std::min(cursum,curmin);
            cursum+=mid;
            if(cursum>0){
                toright.push_back({-curmin,cursum});
                cursum=0;curmin=0;
            }
        }
        std::pair<long long,long long> rightex={-curmin,-cursum};
        //std::cout<<leftex.first<<' '<<leftex.second<<'\n';
        long long lp=0,rp=0,cur=mid;
        while(lp<toleft.size()||rp<toright.size()){
            //std::cout<<lp<<' '<<rp<<"lprp\n";
            if(lp<toleft.size()&&cur>=toleft[lp].first){
                cur+=toleft[lp].second;
                lp++;
            }else if(rp<toright.size()&&cur>=toright[rp].first){
                cur+=toright[rp].second;
                rp++;
            }else{
                cur=-1;
                break;
            }
        }
        if(cur>=std::min(std::max(leftex.first,leftex.second+rightex.first),std::max(leftex.first+rightex.second,rightex.first))){
            upper=mid;
        }else{
            lower=mid;
        }
    }
    //upper/=2;//towards each other
    std::cout<<(upper+2*t-1)/(2*t)<<'\n';
}

Compilation message (stderr)

sparklers.cpp: In function 'int main()':
sparklers.cpp:56:17: 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]
   56 |         while(lp<toleft.size()||rp<toright.size()){
      |               ~~^~~~~~~~~~~~~~
sparklers.cpp:56:35: 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]
   56 |         while(lp<toleft.size()||rp<toright.size()){
      |                                 ~~^~~~~~~~~~~~~~~
sparklers.cpp:58:18: 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]
   58 |             if(lp<toleft.size()&&cur>=toleft[lp].first){
      |                ~~^~~~~~~~~~~~~~
sparklers.cpp:61:24: 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]
   61 |             }else if(rp<toright.size()&&cur>=toright[rp].first){
      |                      ~~^~~~~~~~~~~~~~~

• Subtask 1: 0 / 30
• Subtask 2: 0 / 20
• Subtask 3: 0 / 50