Submission #1129548

#	Time	Username	Problem	Language	Result	Execution time	Memory
1129548		MMihalev	Closing Time (IOI23_closing)	C++17	83 / 100	1052 ms	50840 KiB

closing

#include "closing.h"
#include<vector>
#include<iostream>
#include<algorithm>
#include<queue>
#include<set>
#include<tuple>
using namespace std;
const int MAX_N=2e5+5;
const long long INF=(1LL<<60);
int n,x,y;
long long k;
vector<pair<int,int>>g[MAX_N];
int ans;
long long bfsdist[MAX_N];
void bfs()
{
    for(int i=0;i<n;i++)bfsdist[i]=INF;
    long long remm=k;
    int curanss=0;

    bfsdist[x]=0;
    bfsdist[y]=0;
    set<pair<long long,int>>q;
    q.insert({0,x});
    q.insert({0,y});

    while(q.size())
    {
        int u,curdist;
        tie(curdist,u)=(*(q.begin()));

        if(remm>=curdist)
        {
            remm-=curdist;
            curanss++;
        }
        else break;

        q.erase({curdist,u});

        for(auto [v,edge]:g[u])
        {
            long long len=bfsdist[u]+edge;
            if(len<bfsdist[v])
            {
                q.erase({bfsdist[v],v});
                bfsdist[v]=len;
                q.insert({bfsdist[v],v});
            }
        }
    }

    ans=max(ans,curanss);
}

bool onpath[MAX_N];
int parent[MAX_N];
long long paredge[MAX_N];
long long depth[MAX_N];
long long curdist;
long long distxy;
long long rem;
int curans;
multiset<long long>s;

vector<long long>best[MAX_N][2];
long long dp[2][MAX_N][3];
int sz;

void dfs(int u,int par)
{
    for(auto [v,edge]:g[u])
    {
        if(v==par)continue;

        depth[v]=depth[u]+edge;
        parent[v]=u;
        paredge[v]=edge;

        dfs(v,u);
    }
}
void spread(int u,int par,long long dfsdist)
{
    if(dfsdist)s.insert(curdist+dfsdist);
    else
    {
        rem-=curdist;
        curans++;
    }

    for(auto [v,edge]:g[u])
    {
        if(onpath[v] or v==par)continue;

        spread(v,u,dfsdist+edge);
    }
}
void solve()
{
    rem=k;
    curans=0;

    for(int i=0;i<n;i++)
    {
        onpath[i]=0;
    }

    sz=0;

    parent[x]=-1;
    paredge[x]=0;
    depth[x]=0;
    dfs(x,-1);

    distxy=depth[y];
    curdist=0;
    bool changed=0;

    int u=y;
    while(u!=-1)
    {
        onpath[u]=1;

        s.clear();
        spread(u,parent[u],0);

        ++sz;

        int all=s.size()+1;

        best[sz][0].clear();
        best[sz][0].push_back(0);

        for(auto D:s)
        {
            best[sz][0].push_back(best[sz][0].back()+D);
        }

        best[sz][1].resize(2*all);
        best[sz][1][0]=0;

        for(long long take=1;take<=2*all-1;take++)
        {
            best[sz][1][take]=INF;

            for(long long subtake=0;subtake<=min((long long)best[sz][0].size()-1,take);subtake++)
            {
                if(take-subtake<=subtake+1)best[sz][1][take]=min(best[sz][1][take],best[sz][0][subtake]+(take-subtake)*(-curdist+(distxy-curdist)));
            }
        }

        curdist+=(changed==0 ? +paredge[u] : -paredge[u]);
        if(changed==0)
        {
            if(curdist>distxy-curdist)
            {
                curdist=distxy-curdist;
                changed=1;
            }
        }
        u=parent[u];
    }

    if(rem<0)return;

    for(int take=1;take<=2*n-curans;take++)
    {
        for(int f=0;f<3;f++)
        {
            dp[0][take][f]=INF;
            dp[1][take][f]=INF;
        }
    }

    for(int i=1;i<=sz;i++)
    {
        for(int take=1;take<=2*n-curans;take++)
        {
            for(int f=0;f<3;f++)
            {
                for(int subtake=0;subtake<=min(take,(int)best[i][(f==1)].size()-1);subtake++)
                {
                    dp[i&1][take][f]=min(dp[i&1][take][f],min(dp[(i-1)&1][take-subtake][f],(f>0 ? dp[(i-1)&1][take-subtake][f-1] : INF))+best[i][(f==1)][subtake]);
                }
            }
        }

        for(int take=1;take<=2*n-curans;take++)
        {
            for(int f=0;f<3;f++)
            {
                dp[(i-1)&1][take][f]=INF;
            }
        }
    }

    for(int take=2*n-curans;take>=0;take--)
    {
        if(min(dp[sz&1][take][0],min(dp[sz&1][take][1],dp[sz&1][take][2]))<=rem)
        {
            curans+=take;
            break;
        }
    }

    ans=max(ans,curans);
}
int max_score(int N, int X, int Y, long long K,std::vector<int> U, std::vector<int> V, std::vector<int> W)
{
    ans=2;n=N;x=X;y=Y;k=K;

    for(int i=0;i<n;i++)g[i].clear();

    for(int i=0;i<n-1;i++)
    {
        int u,v,w;
        u=U[i];
        v=V[i];
        w=W[i];
        g[u].push_back({v,w});
        g[v].push_back({u,w});
    }

    bfs();

    solve();

    return ans;
}

• Subtask 0: 0 / 0
• Subtask 1: 8 / 8
• Subtask 2: 9 / 9
• Subtask 3: 12 / 12
• Subtask 4: 14 / 14
• Subtask 5: 9 / 9
• Subtask 6: 11 / 11
• Subtask 7: 10 / 10
• Subtask 8: 10 / 10
• Subtask 9: 0 / 17