Submission #223885

#	Time	Username	Problem	Language	Result	Execution time	Memory
223885		medk	Capital City (JOI20_capital_city)	C++14	11 / 100	3076 ms	47076 KiB

capital_city

#include <bits/stdc++.h>

#define ll long long
#define pb push_back
#define x first
#define y second
#define all(u) u.begin(),u.end()
#define sz(u) (int)(u.size())
#define INF (int)(1e9)

using namespace std;

const int MAXN=2e5+5;

int n,k,ans=INF;
vector<vector<int>> tr(MAXN),grp(MAXN),cd(MAXN);
int col[MAXN],subsz[MAXN],parcd[MAXN],par[MAXN],dpth[MAXN],in[MAXN],dpthcd[MAXN];
bool blocked[MAXN];
int lca[MAXN][20];
int root=-1;
vector<int> eul;

void calc_sz(int u, int pr)
{
    subsz[u]=1;
    for(int v:tr[u])
    {
        if(v==pr || blocked[v]) continue;
        calc_sz(v,u);
        subsz[u]+=subsz[v];
    }
}

int find_centroid(int u, int pr, int tar)
{
    for(int v:tr[u])
    {
        if(v==pr || blocked[v]) continue;
        if(subsz[v]>tar) return find_centroid(v,u,tar);
    }
    return u;
}

void decomp(int u, int pr, int d=0)
{
    memset(subsz,0,sizeof(subsz));
    calc_sz(u,pr);
    int centroid=find_centroid(u,pr,subsz[u]/2);
    blocked[centroid]=1;
    parcd[centroid]=pr;
    dpthcd[centroid]=d;
    if(pr==-1) root=centroid;
    else
    {
        cd[centroid].pb(pr);
        cd[pr].pb(centroid);
    }
    for(int v:tr[centroid])
    {
        if(blocked[v]) continue;
        decomp(v,centroid,d+1);
    }
}

void makeul(int u, int pr, int d)
{
    in[u]=sz(eul);
    eul.pb(u);
    dpth[u]=d;
    par[u]=pr;
    d++;
    for(int v:tr[u])
    {
        if(pr==v) continue;
        makeul(v,u,d);
        eul.pb(u);
    }
}

int getlca(int u, int v)
{
    int l=in[u], r=in[v];
    if(l>r) swap(l,r);
    int lg=log2(r-l+1);
    if(dpth[lca[l][lg]]<=dpth[lca[r-(1<<lg)+1][lg]]) return lca[l][lg];
    return lca[r-(1<<lg)+1][lg];
}

int lcacd(int u, int v)
{
    if(dpthcd[u]==dpthcd[v])
    {
        if(u==v) return u;
        else return lcacd(parcd[u],parcd[v]);
    }
    if(dpthcd[v]<dpthcd[u]) swap(u,v);
    return lcacd(u,parcd[v]);
}

void solve(int rt, int pr)
{
    vector<bool> viscol(k,0);
    vector<int> visver(n,0);
    int lc=rt, used=0;
    queue<int> q;
    q.push(rt);
    visver[rt]=1;
    bool bug=0;
    while(!q.empty())
    {
        int u=q.front(); q.pop();
        visver[u]=2;
        if(u!=lc)
        {
            int mypar=par[u];
            if(visver[mypar]==0 && !viscol[col[mypar]] && col[mypar]!=col[u])
            {
                if(lcacd(mypar,rt)!=rt)
                {
                    bug=1;
                    break;
                }
                q.push(mypar);
                visver[mypar]=1;
            }
        }
        if(viscol[col[u]]) continue;
        viscol[col[u]]=1;
        used++;
        for(int v:grp[col[u]])
        {
            if(v==u) continue;
            int newlc=getlca(lc,v);
            if(newlc!=lc)
            {
                if(visver[lc]==2)
                {
                    if(lcacd(par[lc],rt)!=rt)
                    {
                        bug=1;
                        break;
                    }
                    q.push(par[lc]);
                    visver[par[lc]]=1;
                }
                lc=newlc;
            }
            if(lcacd(v,rt)!=rt)
            {
                bug=1;
                break;
            }
            visver[v]=1;
            q.push(v);
        }
        if(bug) break;
    }
    if(!bug) ans=min(ans,used);
    for(int v:cd[rt])
    {
        if(v==pr) continue;
        solve(v,rt);
    }
}

int main()
{
    //freopen("test.in","r",stdin);
    ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
    cin>>n>>k;
    for(int i=0;i<n-1;i++)
    {
        int u,v; cin>>u>>v;
        u--,v--;
        tr[u].pb(v);
        tr[v].pb(u);
    }
    for(int i=0;i<n;i++)
    {
        cin>>col[i];
        col[i]--;
        grp[col[i]].pb(i);
    }
    decomp(0,-1);
    makeul(0,-1,0);
    for(int i=0;i<sz(eul);i++) lca[i][0]=eul[i];
    for(int j=1;j<20;j++)
        for(int i=0;i+(1<<j)<=sz(eul);i++)
            lca[i][j]=(dpth[lca[i][j-1]]<=dpth[lca[i+(1<<(j-1))][j-1]]?lca[i][j-1]:lca[i+(1<<(j-1))][j-1]);
    solve(root,-1);
    cout<<ans-1<<'\n';
}

• Subtask 1: 1 / 1
• Subtask 2: 10 / 10
• Subtask 3: 0 / 30
• Subtask 4: 0 / 59