Submission #1030361

#	Time	Username	Problem	Language	Result	Execution time	Memory
1030361		happy_node	Carnival Tickets (IOI20_tickets)	C++17	41 / 100	610 ms	121224 KiB

tickets

#include "tickets.h"
#include <bits/stdc++.h>
using namespace std;

typedef long long ll;

const int MX=1505, of=1505;

ll dp[MX][2*MX], par[MX][2*MX];

int cur[MX];

long long find_maximum(int k, std::vector<std::vector<int>> d) {
        int N=d.size();
        int M=d[0].size();      

        if(k==M) {
                vector<array<int,3>> vals;

                for(int i=0;i<N;i++) {
                        for(int j=0;j<M;j++) {
                                vals.push_back({d[i][j],i,j});
                        }
                }

                sort(vals.begin(),vals.end());

                ll ans=0;
                for(int i=0;i<N*M/2;i++) {
                        ans-=vals[i][0];
                        cur[vals[i][1]]++;
                }
                for(int i=N*M/2;i<N*M;i++) {
                        ans+=vals[i][0];
                }

                vector<pair<int,int>> v;

                for(int i=0;i<N;i++) 
                        v.push_back({cur[i]-1,i});

                // for each k, we try to find N/2 nodes with largest cur_i and set it to fill in the negatives, and other N/2 o fill in the positives
                
                vector<int> fr(N), bk(N,M-1);
                vector<vector<int>> s(N,vector<int>(M,-1));

                for(int x=0;x<k;x++) {
                        sort(v.rbegin(),v.rend());
                        for(int j=0;j<N/2;j++) {
                                auto &[y,i]=v[j];
                                s[i][fr[i]]=x;
                                fr[i]++;
                                y--;
                        }
                        for(int j=N/2;j<N;j++) {
                                auto &[y,i]=v[j];
                                s[i][bk[i]]=x;
                                bk[i]--;
                        }
                }

                allocate_tickets(s);

                return ans;
        }

        vector<pair<int,int>> v;
        for(int i=0;i<N;i++) v.push_back({d[i].front(),d[i].back()}); 
        
        for(int i=0;i<MX;i++)
                for(int j=0;j<2*MX;j++)
                        dp[i][j]=-1e18;

        dp[0][0+of]=0;
        for(int i=0;i<N;i++) {
                for(int j=-N;j<=N;j++) {
                        if(dp[i][j+of]==-1e18) continue;

                        if(dp[i][j+of]+v[i].second>dp[i+1][j+1+of]) {
                                dp[i+1][j+1+of]=dp[i][j+of]+v[i].second;
                                par[i+1][j+1+of]=1;
                        } 
                        if(dp[i][j+of]-v[i].first>dp[i+1][j-1+of]) {
                                dp[i+1][j-1+of]=dp[i][j+of]-v[i].first;
                                par[i+1][j-1+of]=-1;
                        }
                }
        }

        vector<vector<int>> s(N,vector<int>(M,-1));

        int cur=N, bal=0;
        while(cur>0) {
                if(par[cur][bal+of]>0) s[cur-1].back()=0;
                else s[cur-1].front()=0;
                bal-=par[cur][bal+of];
                cur--;
        }

        allocate_tickets(s);

        return dp[N][0+of];
}

• Subtask 1: 11 / 11
• Subtask 2: 16 / 16
• Subtask 3: 0 / 14
• Subtask 4: 14 / 14
• Subtask 5: 0 / 12
• Subtask 6: 0 / 23
• Subtask 7: 0 / 10