Submission #919383

#	Time	Username	Problem	Language	Result	Execution time	Memory
919383		imarn	Mergers (JOI19_mergers)	C++14	100 / 100	1384 ms	193548 KiB

mergers

#include<bits/stdc++.h>
#define ll long long
#define pii pair<int,int>
#define pll pair<ll,ll>
#define f first
#define s second
#define pb push_back
#define all(x) x.begin(),x.end()
#define vi vector<int>
#define vvi vector<vi>
#define vp vector<pii>
using namespace std;
const int N=5e5+5;
vector<int>g[N],gr[N];
set<int>gg[N];
int dep[N],up[N][21],pr[N],d[N],t=0;
int get(int r){
    return pr[r]==r?r:pr[r]=get(pr[r]);
}
void dfs(int u,int p,int l){
    dep[u]=l;up[u][0]=p;d[u]=++t;
    for(int i=1;i<=20;i++)up[u][i]=up[up[u][i-1]][i-1];
    for(auto v:g[u]){
        if(v==p)continue;
        dfs(v,u,l+1);
    }
}
int qr(int a,int b){
    if(dep[a]>dep[b])swap(a,b);
    for(int i=20;i>=0;i--)if(dep[b]-(1<<i)>=dep[a])b=up[b][i];
    if(a==b)return a;
    for(int i=20;i>=0;i--)if(up[a][i]!=up[b][i])a=up[a][i],b=up[b][i];
    return up[a][0];
}
bool cmp(int a,int b){
    return d[a]<d[b];
}
int main(){
    ios_base::sync_with_stdio(0);cin.tie(0);
    int n,k;cin>>n>>k;iota(pr,pr+n+1,0);
    for(int i=1;i<=n-1;i++){
        int u,v;cin>>u>>v;g[u].pb(v);g[v].pb(u);
    }dfs(1,1,0);
    for(int i=1,x;i<=n;i++)cin>>x,gr[x].pb(i);
    for(int i=1;i<=k;i++){
        sort(gr[i].begin(),gr[i].end(),cmp);
        for(int j=1;j<gr[i].size();j++){
            int lca=qr(gr[i][j-1],gr[i][j]);
            int u=gr[i][j-1],v=gr[i][j];
            while(get(u)!=get(lca)){
                int uu=up[get(u)][0];
                pr[get(u)]=get(uu);u=uu;
            }
            while(get(v)!=get(lca)){
                int vv=up[get(v)][0];
                pr[get(v)]=get(vv);v=vv;
            }
        }
    }
    for(int i=1;i<=n;i++){
        for(auto it : g[i]){
            if(get(it)==get(i))continue;
            gg[get(it)].insert(get(i));
            gg[get(i)].insert(get(it));
        }
    }int ct=0;
    for(int i=1;i<=n;i++)if(gg[i].size()==1)ct++;
    cout<<(ct+1)/2;
}

Compilation message (stderr)

mergers.cpp: In function 'int main()':
mergers.cpp:47:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   47 |         for(int j=1;j<gr[i].size();j++){
      |                     ~^~~~~~~~~~~~~

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