Submission #1039546

#	Time	Username	Problem	Language	Result	Execution time	Memory
1039546		vjudge1	Mergers (JOI19_mergers)	C++17	100 / 100	850 ms	164864 KiB

mergers

#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define ld long double
#define pii pair<int,int>
#define pll pair<ll,ll>
#define fi first
#define se second
const int maxN=5e5+5,LG=__lg(maxN)+5;
const ll inf=2e18;
int n,k,a[maxN+1],num[maxN+1],timer=0,h[maxN+1],up[maxN+1][LG+1],f[maxN+1];
vector<int> adj[maxN+1],vec[maxN+1],nadj[maxN+1];
void dfs(int u)
{
    num[u]=++timer;
    for(auto v:adj[u])
    {
        if(v==up[u][0])
        {
            continue;
        }
        up[v][0]=u;
        h[v]=h[u]+1;
        for(int j=1;j<=LG;j++)
        {
            up[v][j]=up[up[v][j-1]][j-1];
        }
        dfs(v);
    }
}
int lca(int u,int v)
{
    if(h[u]<h[v])
    {
        swap(u,v);
    }
    for(int j=LG;j>=0;j--)
    {
        if(h[up[u][j]]>=h[v])
        {
            u=up[u][j];
        }
    }
    if(u==v)
    {
        return u;
    }
    for(int j=LG;j>=0;j--)
    {
        if(up[u][j]!=up[v][j])
        {
            u=up[u][j];
            v=up[v][j];
        }
    }
    return up[u][0];
}
void dfs1(int u)
{
    for(auto v:adj[u])
    {
        if(v!=up[u][0])
        {
            dfs1(v);
            f[u]+=f[v];
        }
    }
}
void dfs2(int u,int p)
{
    for(auto v:adj[u])
    {
        if(v!=up[u][0])
        {
            int nv=p;
            if(!f[v])
            {
                //cout<<u<<" "<<v<<'\n';
                nadj[v].push_back(p);
                nadj[p].push_back(v);
                nv=v;
            }
            dfs2(v,nv);
        }
    }
}
int main()
{
    //freopen("","r",stdin);
    //freopen("","w",stdout);
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    cin>>n>>k;
    for(int i=1;i<n;i++)
    {
        int u,v;
        cin>>u>>v;
        adj[u].push_back(v);
        adj[v].push_back(u);
    }
    h[1]=1;
    dfs(1);
    for(int i=1;i<=n;i++)
    {
        cin>>a[i];
        vec[a[i]].push_back(i);
    }
    for(int i=1;i<=k;i++)
    {
        sort(vec[i].begin(),vec[i].end(),[&](int x,int y)
        {
            return num[x]<num[y];
        });
        int len=vec[i].size();
        if(len==1)
        {
            continue;
        }
        for(int j=0;j<len;j++)
        {
            int u=vec[i][j],v=vec[i][(j+1)%len];
            f[u]++;
            f[lca(u,v)]--;
        }
    }
    dfs1(1);
    dfs2(1,1);
    int cnt=0;
    for(int i=1;i<=n;i++)
    {
        cnt+=(nadj[i].size()==1);
    }
    cout<<(cnt+1)/2;
}

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