Submission #986001

#	Time	Username	Problem	Language	Result	Execution time	Memory
986001		andrei_boaca	Mergers (JOI19_mergers)	C++17	100 / 100	1694 ms	210528 KiB

mergers

#include <bits/stdc++.h>

using namespace std;
typedef pair<int,int> pii;
int n,K,par[500005];
int nr[500005],dp[21][500005],niv[500005],in[500005],out[500005],timp;
vector<int> muchii[500005];
vector<int> culs[500005];
int grad[500005];
map<pii,int> ban;
bool isancestor(int a,int b)
{
    return in[a]<=in[b]&&out[a]>=out[b];
}
int LCA(int a,int b)
{
    if(niv[a]>niv[b])
        swap(a,b);
    if(isancestor(a,b))
        return a;
    for(int i=20;i>=0;i--)
        if(dp[i][a]!=0&&!isancestor(dp[i][a],b))
            a=dp[i][a];
    return par[a];
}
void initdfs(int nod)
{
    timp++;
    in[nod]=timp;
    dp[0][nod]=par[nod];
    for(int i=1;i<=20;i++)
        dp[i][nod]=dp[i-1][dp[i-1][nod]];
    for(int i:muchii[nod])
        if(i!=par[nod])
        {
            par[i]=nod;
            niv[i]=niv[nod]+1;
            initdfs(i);
        }
    out[nod]=timp;
}
void calc(int nod)
{
    for(int i:muchii[nod])
        if(i!=par[nod])
        {
            calc(i);
            nr[nod]+=nr[i];
        }
    if(nr[nod]==0&&nod!=1)
    {
        ban[{nod,par[nod]}]=1;
        ban[{par[nod],nod}]=1;
    }
}
int comp[500005],nrcomp;
void dfs(int nod)
{
    comp[nod]=nrcomp;
    for(int i:muchii[nod])
        if(!comp[i])
            if(ban.count({nod,i})==0)
                dfs(i);
}
int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    cin>>n>>K;
    for(int i=1;i<n;i++)
    {
        int a,b;
        cin>>a>>b;
        muchii[a].push_back(b);
        muchii[b].push_back(a);
    }
    for(int i=1;i<=n;i++)
    {
        int x;
        cin>>x;
        culs[x].push_back(i);
    }
    initdfs(1);
    for(int i=1;i<=K;i++)
    {
        for(int j=1;j<culs[i].size();j++)
        {
            int a=culs[i][0];
            int b=culs[i][j];
            int lca=LCA(a,b);
            nr[a]++;
            nr[b]++;
            nr[lca]-=2;
        }
    }
    calc(1);
    if(ban.empty())
    {
        cout<<0;
        return 0;
    }
    for(int i=1;i<=n;i++)
        if(!comp[i])
        {
            nrcomp++;
            dfs(i);
        }
    for(auto z:ban)
    {
        pii p=z.first;
        if(p.first>p.second)
            continue;
        int a=comp[p.first];
        int b=comp[p.second];
        grad[a]++;
        grad[b]++;
    }
    int ans=0;
    for(int i=1;i<=nrcomp;i++)
        if(grad[i]==1)
            ans++;
    cout<<ans/2+ans%2;
    return 0;
}

Compilation message (stderr)

mergers.cpp: In function 'int main()':
mergers.cpp:86:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   86 |         for(int j=1;j<culs[i].size();j++)
      |                     ~^~~~~~~~~~~~~~~

• Subtask 1: 10 / 10
• Subtask 2: 24 / 24
• Subtask 3: 14 / 14
• Subtask 4: 22 / 22
• Subtask 5: 30 / 30