Submission #919068

#	Time	Username	Problem	Language	Result	Execution time	Memory
919068		12345678	Mergers (JOI19_mergers)	C++17	0 / 100	49 ms	31944 KiB

mergers

#include <bits/stdc++.h>

using namespace std;

const int nx=5e5+5, kx=19;
int lvl[nx], pa[nx][kx], n, k, u, v, s[nx], l[nx], rem[nx], cnt, on[nx], ed[nx], sg, ans, t[nx];
vector<int> d[nx];

void dfs(int u, int p)
{
    lvl[u]=lvl[p+1]; pa[u][0]=p;
    for (int i=1; i<kx; i++) pa[u][i]=pa[pa[u][i-1]][i-1];
    for (auto v:d[u]) if (v!=p) dfs(v, u);
}

int lca(int u, int v)
{
    if (lvl[u]>lvl[v]) swap(u, v);
    for (int i=kx-1; i>=0; i--) if (lvl[pa[v][i]]>=lvl[u]) v=pa[v][i];
    if (u==v) return u;
    for (int i=kx-1; i>=0; i--) if (pa[u][i]!=pa[v][i]) u=pa[u][i], v=pa[v][i];
    return pa[u][0];
}

void dfs2(int u, int p)
{
    if (l[s[u]]==0) l[s[u]]=u;
    else l[s[u]]=lca(l[s[u]], u);
    for (auto v:d[u]) if (v!=p) dfs2(v, u);
}

void dfs3(int u, int p)
{
    for (auto v:d[u]) if (v!=p) dfs3(v, u);
    if (on[s[u]]++==0) cnt++;
    cnt-=rem[u];
    if (cnt==0&&u!=1) ed[u]=1, sg=1;
}

void dfs4(int u, int p, int c)
{
    for (auto v:d[u])
    {
        if (v==p) continue;
        if (on[v]) 
        {
            t[u]++;
            dfs4(v, u, v);
            if (t[v]==0) ans++;
        }
        else dfs4(v, u, c);
    }
}

int main()
{
    cin.tie(NULL)->sync_with_stdio(false);
    cin>>n>>k;
    for (int i=1; i<n; i++) cin>>u>>v, d[u].push_back(v), d[v].push_back(u);
    for (int i=1; i<=n; i++) cin>>s[i];
    dfs(1, 1);
    dfs2(1, 1);
    for (int i=1; i<=k; i++) rem[l[i]]++;
    dfs3(1, 1);
    if (!sg) return cout<<0, 0;
    dfs4(1, 1, 1);
    //for (int i=1; i<=n; i++) cout<<i<<' '<<ed[i]<<'\n';
    ans+=(t[1]==1);
    cout<<(ans+1)/2;
}

/*
3 3
1 2
2 3
1 2 3

4 4
1 2
2 3
2 4
1 2 3 4
*/

• Subtask 1: 0 / 10
• Subtask 2: 0 / 24
• Subtask 3: 0 / 14
• Subtask 4: 0 / 22
• Subtask 5: 0 / 30