Submission #862245

#	Time	Username	Problem	Language	Result	Execution time	Memory
862245		Hanksburger	Meetings 2 (JOI21_meetings2)	C++17	100 / 100	266 ms	43160 KiB

meetings2

#include <bits/stdc++.h>
using namespace std;
int par[200005][20], sz[200005], dep[200005], ans[200005], n, c, x, y, ind, res=1;
vector<pair<int, int> > vec;
vector<int> adj[200005];
void dfs(int u, int p)
{
    sz[u]=1;
    for (int v:adj[u])
    {
        if (v!=p)
        {
            dfs(v, u);
            sz[u]+=sz[v];
        }
    }
    bool ok=1;
    for (int v:adj[u])
    {
        if (sz[v]>n/2)
        {
            ok=0;
            break;
        }
    }
    if (ok && n-sz[u]<=n/2)
        c=x=y=u;
}
void dfs2(int u, int p)
{
    par[u][0]=p;
    for (int i=1; i<20; i++)
        par[u][i]=par[par[u][i-1]][i-1];
    sz[u]=1;
    for (int v:adj[u])
    {
        if (v!=p)
        {
            dep[v]=dep[u]+1;
            dfs2(v, u);
            sz[u]+=sz[v];
        }
    }
}
int lca(int u, int v)
{
    if (dep[u]<dep[v])
        swap(u, v);
    if (dep[u]>dep[v])
    {
        int diff=dep[u]-dep[v];
        for (int i=0; i<20; i++)
            if (diff&(1<<i))
                u=par[u][i];
    }
    if (u==v)
        return u;
    for (int i=19; i>=0; i--)
        if (par[u][i]!=par[v][i])
            u=par[u][i], v=par[v][i];
    return par[u][0];
}
int len(int u, int v)
{
    return dep[u]+dep[v]-dep[lca(u, v)]*2;
}
int main()
{
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    cin >> n;
    for (int i=1; i<n; i++)
    {
        int u, v;
        cin >> u >> v;
        adj[u].push_back(v);
        adj[v].push_back(u);
    }
    dfs(1, 1);
    dfs2(c, c);
    for (int i=1; i<=n; i++)
        if (i!=c)
            vec.push_back({min(sz[i], n-sz[i]+1), i});
    sort(vec.begin(), vec.end(), greater<pair<int, int> >());
    for (int i=n; i>=1; i--)
    {
        if (i&1)
        {
            ans[i]=1;
            continue;
        }
        while (ind<vec.size() && vec[ind].first>=i/2)
        {
            int u=vec[ind].second;
            int xy=len(x, y);
            int ux=len(u, x);
            int uy=len(u, y);
            if (ux>=uy && ux>xy)
            {
                y=u;
                res=ux+1;
            }
            else if (uy>ux && uy>xy)
            {
                x=u;
                res=uy+1;
            }
            ind++;
        }
        ans[i]=res;
    }
    for (int i=1; i<=n; i++)
        cout << ans[i] << '\n';
}

Compilation message (stderr)

meetings2.cpp: In function 'int main()':
meetings2.cpp:93:19: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   93 |         while (ind<vec.size() && vec[ind].first>=i/2)
      |                ~~~^~~~~~~~~~~

• Subtask 1: 4 / 4
• Subtask 2: 16 / 16
• Subtask 3: 80 / 80