Submission #1003967

#	Time	Username	Problem	Language	Result	Execution time	Memory
1003967		vjudge1	Pastiri (COI20_pastiri)	C++17	8 / 100	1048 ms	141300 KiB

pastiri

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

#define N 500010
#define M 50
#define LOG 22
#define INFLL 2000000000000000020
#define pb push_back

typedef long long ll;
typedef pair<ll,ll> pll;

vector<ll>resp;
ll vet[N];
ll pai[N][LOG];
vector<ll>grafo[N];
ll n,k;
vector<ll>ativos;
vector<ll>aux;
map<ll,ll>dist;
ll lca;
ll lvl[N];

void DFS(ll u)
{
    for(auto v : grafo[u])
    {
        if(lvl[v])
            continue;
        pai[v][0]=u;
        lvl[v]=lvl[u]+1;
        DFS(v);
    }
    return;
}

void build()
{
    ll i,j;
    lvl[1]=1;
    pai[1][0]=1;
    DFS(1);
    for(i=1;i<LOG;i++)
    {
        for(j=1;j<=n;j++)
        {
            pai[j][i]=pai[pai[j][i-1]][i-1];
        }
    }
    return;
}

ll LCA(ll u,ll v)
{
    ll i,diff=abs(lvl[u]-lvl[v]);
    if(lvl[u]<lvl[v])
        swap(u,v);
    for(i=LOG-1;i>=0;i--)
    {
        if((diff&(1<<i)))
        {
            u=pai[u][i];
        }
    }
    if(u==v)
        return u;
    for(i=LOG-1;i>=0;i--)
    {
        if(pai[u][i]!=pai[v][i])
        {
            u=pai[u][i];
            v=pai[v][i];
        }
    }
    return pai[u][0];
}

ll DIST(ll u,ll v)
{
    lca=LCA(u,v);
    return lvl[u]+lvl[v]-2*lvl[lca];
}

void test()
{
    ll i,ret,mx=0,who,md,maior=0,d,j;
    for(i=1;i<=n;i++)
    {
        d=INFLL;
        for(j=0;j<k;j++)
        {
            d=min(d,DIST(i,vet[j]));
        }
        mx=0;
        for(auto x : ativos)
        {
            ret=DIST(i,x);
            mx+=(bool)(ret==d);
        }
        if(maior<mx)
        {
            md=d;
            who=i;
            maior=mx;
        }
    }
    d=md;
    for(auto x : ativos)
    {
        if(DIST(who,x)!=d)
            aux.pb(x);
    }
    ativos.clear();
    for(auto x : aux)
    {
        ativos.pb(x);
    }
    aux.clear();
    resp.pb(who);
    return;
}

int main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
   
    ll u,v,i=0,ans,sz;

    cin >> n >> k;
    while(i<n-1)
    {
        cin >> u >> v;
        grafo[u].pb(v);
        grafo[v].pb(u);
        i++;
    }
    i=0;
    while(i<k)
    {
        cin >> vet[i];
        ativos.pb(vet[i]);
        i++;
    }
    if(k<=15 || n<=2000)
    {
        build();
        while(!ativos.empty())
        {
            test();
        }
        sz=(ll)(resp.size());
        cout << sz << endl;
        for(i=0;i<sz;i++)
        {
            cout << resp[i] << ((i==sz-1) ? '\n' : ' ');
        }
        return 0;
    }
    sort(vet,vet+k);
    vet[k]=vet[k-1];
    for(i=0;i<k;i++)
    {
        if((vet[i+1]-vet[i])%2)
        {
            resp.pb(vet[i]);
        }else
        {
            resp.pb((vet[i+1]+vet[i])/2);
            i++;
        }
    }
    sz=(ll)(resp.size());
    cout << sz << endl;
    for(i=0;i<sz;i++)
    {
        cout << resp[i] << ((i==sz-1) ? '\n' : ' ');
    }

    return 0;
}

Compilation message (stderr)

pastiri.cpp: In function 'int main()':
pastiri.cpp:129:16: warning: unused variable 'ans' [-Wunused-variable]
  129 |     ll u,v,i=0,ans,sz;
      |                ^~~
pastiri.cpp: In function 'void test()':
pastiri.cpp:110:9: warning: 'md' may be used uninitialized in this function [-Wmaybe-uninitialized]
  110 |         if(DIST(who,x)!=d)
      |         ^~

• Subtask 1: 8 / 8
• Subtask 2: 0 / 18
• Subtask 3: 0 / 23
• Subtask 4: 0 / 51