Submission #565812

#	Time	Username	Problem	Language	Result	Execution time	Memory
565812		shahriarkhan	Village (BOI20_village)	C++14	50 / 100	142 ms	39840 KiB

Village

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

const int MX = 1e5 + 5 , INF = 1e9 + 5 , LG = 25 ;

int dp[MX][2] , mn[MX] ;

vector<int> adj[MX] ;

vector<pair<int,int> > pick[MX][2] ;

void dfs(int s , int p)
{
    int sum = 0 , good = 0 , leaf = 1 , rd = 0 , pos = 0 , idx = 0 ;
    dp[s][0] = 0 , dp[s][1] = INF ;
    for(int t : adj[s])
    {
        if(t==p) continue ;
        dfs(t,s) , leaf = 0 ;
        dp[s][0] = min(dp[s][0] + dp[t][1] , INF) , pick[s][0].push_back({t,1}) ;
        if((dp[t][0]+2)<=dp[t][1])
        {
            sum += dp[t][0] + 2 , pick[s][1].push_back({t,0}) , ++pos ;
            good = 1 ;
        }
        else
        {
            if(dp[t][0]<dp[t][1])
            {
                rd = t ;
                idx = pos ;
            }
            sum += dp[t][1] , pick[s][1].push_back({t,1}) , ++pos;
        }
    }
    if(!leaf)
    {
        if(!good)
        {
            if(rd)
            {
                pick[s][1].erase(pick[s][1].begin()+idx) ;
                pick[s][1].push_back({rd,0}) ;
                sum -= dp[rd][1] ;
                sum += dp[rd][0] + 2 ;
            }
            else
            {
                pick[s][1][0].second = 2 ;
                sum += 2 ;
            }
        }
        dp[s][1] = sum ;
    }
}

void build(int s , int c)
{
    if(c==2) c = 1 ;
    for(pair<int,int> p : pick[s][c])
    {
        build(p.first,p.second) ;
        if(p.second!=1) swap(mn[p.first],mn[s]) ;
    }
}

struct centroid_tree
{
    long long cst = 0 ;
    int N = 0 ;
    vector<int> S ;
    vector<vector<int> > adj ;
    vector<int> sub , centroid , mx , par ;
    void init(int n , vector<int> f[])
    {
        N = n ;
        adj = vector<vector<int> > (n+2) ;
        sub = vector<int> (n+2,0) ;
        mx = vector<int> (n+2,0) ;
        par = vector<int> (n+2,0) ;
        centroid = vector<int> (n+2,0) ;
        for(int i = 1 ; i <= n ; ++i)
        {
            mx[i] = i ;
            for(int j : f[i])
            {
                adj[i].push_back(j) ;
            }
        }
        find_ans() ;
    }
    void find_siz(int s , int p)
    {
        sub[s] = 1 ;
        for(int t : adj[s])
        {
            if(t==p) continue ;
            if(centroid[t]) continue ;
            find_siz(t,s) ;
            sub[s] += sub[t] ;
        }
        for(int t : adj[s])
        {
            if(t==p) continue ;
            cst += min(sub[t],N-sub[t]) ;
        }
    }
    int find_centroid(int s , int p , int n)
    {
        for(int t : adj[s])
        {
            if(t==p) continue ;
            if(centroid[t]) continue ;
            if(sub[t]>(n/2)) return find_centroid(t,s,n) ;
        }
        return s ;
    }

    void topsort(int s , int p)
    {
        for(int t : adj[s])
        {
            if(t==p) continue ;
            topsort(t,s) ;
        }
        S.push_back(s) ;
    }
    void find_ans()
    {
        find_siz(1,0) ;
        int C = find_centroid(1,0,sub[1]) ;
        topsort(C,0) ;
        reverse(S.begin(),S.end()) ;
        for(int i = 0 ; i < (N/2) ; ++i)
        {
            swap(mx[S[i]],mx[S[(i+(N/2))%N]]) ;
        }
        if((N&1) && (N>=2)) swap(mx[S[N-2]],mx[S[N-1]]) ;
    }
};

int main()
{
    int n ;
    scanf("%d",&n) ;
    for(int i = 1 ; i < n ; ++i)
    {
        int x , y ;
        scanf("%d%d",&x,&y) ;
        adj[x].push_back(y) ;
        adj[y].push_back(x) ;
    }
    for(int i = 1 ; i <= n ; ++i)
    {
        mn[i] = i ;
    }
    dfs(1,0) ;
    build(1,1) ;
    centroid_tree C ;
    C.init(n,adj) ;
    printf("%d %lld\n",dp[1][1],2*C.cst) ;
    for(int i = 1 ; i <= n ; ++i)
    {
        printf("%d ",mn[i]) ;
    }
    printf("\n") ;
    for(int i = 1 ; i <= n ; ++i)
    {
        printf("%d ",C.mx[i]) ;
    }
    printf("\n") ;
    return 0 ;
}

Compilation message (stderr)

Village.cpp: In function 'int main()':
Village.cpp:145:10: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
  145 |     scanf("%d",&n) ;
      |     ~~~~~^~~~~~~~~
Village.cpp:149:14: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
  149 |         scanf("%d%d",&x,&y) ;
      |         ~~~~~^~~~~~~~~~~~~~

• Subtask 1: 6 / 12
• Subtask 2: 19 / 38
• Subtask 3: 25 / 50