Submission #595648

#	Time	Username	Problem	Language	Result	Execution time	Memory
595648		czhang2718	Meetings 2 (JOI21_meetings2)	C++17	0 / 100	2 ms	4948 KiB

meetings2

#include "bits/stdc++.h"
using namespace std;

const int N=2e5+1;
int n;
vector<int> adj[N];
int ans[N];
bool vis[N];
int sz[N];

void dfs1(int x, vector<int> &nodes){
    vis[x]=1;
    nodes.push_back(x);
    sz[x]=1;
    for(int k:adj[x]){
        if(vis[k]) continue;
        dfs1(k, nodes);
        sz[x]+=sz[k];
    }
}

void dfs2(int x, int cnt, int &c){
    vis[x]=1;
    for(int k:adj[x]){
        if(vis[k]) continue;
        if(sz[k]>cnt/2){
            dfs2(k, cnt, c);
            if(c) return;
        }
    }
    if(!c) c=x;
}

void dfs3(int x, vector<int>& dp, int d){
    sz[x]=1;
    vis[x]=1;
    for(int k:adj[x]){
        if(vis[k]) continue;
        dfs3(k, dp, d+1);
        sz[x]+=sz[k];
    }
    if(dp.size()<=sz[x]) dp.resize(sz[x]+1);
    // cout << x << " dp[" << sz[x] << "] max= " << d << "\n";
    dp[sz[x]]=max(dp[sz[x]], d);
}

void go(int x){
    // cout << "go " << x << "\n";
    vector<int> nodes;
    dfs1(x, nodes);
    if(nodes.size()==1){
        // vis[nodes.back()]=1;
        return;
    }
    for(int u:nodes) vis[u]=0;

    int c=0;
    dfs2(x, nodes.size(), c);
    // cout << "nodes ";
    // for(int x:nodes) cout << x << vis[x] << " ";
    // cout << "\ncentroid: " << c << "\n";

    for(int u:nodes) if(u!=c) vis[u]=0;
    for(int k:adj[c]) if(!vis[k]) go(k);

    vector<int> mx(nodes.size(), -1), mx2(nodes.size(), -1);

    for(int u:nodes) if(u!=c) vis[u]=0;
    for(int k:adj[c]){
        if(vis[k]) continue;
        vector<int> dp;
        dfs3(k, dp, 1);
        dp.push_back(0);

        for(int i=dp.size()-1; i; i--){
            if(i!=dp.size()-1) dp[i]=max(dp[i], dp[i+1]);
            if(dp[i]>mx[i]) mx2[i]=mx[i], mx[i]=dp[i];
            else if(dp[i]>mx2[i]) mx2[i]=dp[i];
            // cout << mx[i] << mx2[i] << "\n";
        }
    }

    for(int i=1; i<min(n/2+1, (int)nodes.size()); i++){
        if(mx[i]!=-1 && mx2[i]!=-1) ans[2*i]=max(ans[2*i], mx[i]+mx2[i]);
    }
}

int main(){
    cin.tie(0)->sync_with_stdio(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);
    }

    go(1);

    for(int i=1; i<=n; i++){
        if(i&1) cout << "1\n";
        else cout << ans[i]+1 << "\n";
    }
}

Compilation message (stderr)

meetings2.cpp: In function 'void dfs3(int, std::vector<int>&, int)':
meetings2.cpp:42:17: warning: comparison of integer expressions of different signedness: 'std::vector<int>::size_type' {aka 'long unsigned int'} and 'int' [-Wsign-compare]
   42 |     if(dp.size()<=sz[x]) dp.resize(sz[x]+1);
      |        ~~~~~~~~~^~~~~~~
meetings2.cpp: In function 'void go(int)':
meetings2.cpp:76:17: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   76 |             if(i!=dp.size()-1) dp[i]=max(dp[i], dp[i+1]);
      |                ~^~~~~~~~~~~~~

• Subtask 1: 0 / 4
• Subtask 2: 0 / 16
• Subtask 3: 0 / 80