Submission #878909

#	Time	Username	Problem	Language	Result	Execution time	Memory
878909		Mr_Ph	The Xana coup (BOI21_xanadu)	C++17	100 / 100	91 ms	37796 KiB

xanadu

#include<bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
typedef long long ll;
using namespace std;
using namespace __gnu_pbds;
template<class x>
using ordered_set = tree<x, null_type,less<x>, rb_tree_tag,tree_order_statistics_node_update>;
ll mod=(ll)1e9+7;
ll mod1=998244353;
///the defines :)
#define endl '\n'
#define vi vector<int>
#define ent(arr) for(int i=0;i<arr.size();i++)cin>>arr[i];
#define all(arr) arr.begin(),arr.end()
#define allr(arr) arr.rbegin(),arr.rend()
#define sz size()
#define int long long
int dp[200002][2][2];
int n;
vi arr;
vector<vi>adj;
int dfs(int node,int parent,int tg,int cur)
{
    int pog=arr[node]^tg^cur;
   // cout<<node<<" "<<parent<<" "<<pog<<endl;
    if(dp[node][tg][cur]!=-1)return dp[node][tg][cur];
    if(parent&&adj[node].sz==1)return (pog?1e9:cur);
    //odds and even thingies depending on pog, (i forgor)
    int x=adj[node].sz;
    int newdp[x+2][2];
    memset(newdp,1e9,sizeof newdp);
    for(int i=0;i<=x+1;i++)newdp[i][0]=newdp[i][1]=1e9;
    newdp[0][pog]=cur;
    int cnt=0;
    vector<pair<int,int>>xd;
    xd.push_back({0,0});
    for(auto i:adj[node])
    {
        if(i==parent)continue;
        cnt++;
        int e=dfs(i,node,cur,1),e1=dfs(i,node,cur,0);
        for(int j=0;j<2;j++)
            newdp[cnt][j]=min(newdp[cnt-1][j^1]+e,newdp[cnt-1][j]+e1);
    }
   /* cout<<node<<" "<<parent<<" "<<pog<<" "<<tg<<" "<<cur<<" "<<newdp[xd.sz][0]<<endl;
    for(int i=0;i<xd.sz;i++)
    {
        cout<<newdp[i][0]<<" "<<newdp[i][1]<<endl;
    }
    for(auto i:xd)cout<<i.first<<" "<<i.second<<endl;
    cout<<"---"<<endl;
    */
    return dp[node][tg][cur]=newdp[cnt][0];
}
void preprocess() {}
void solve()
{
    cin>>n;
    adj.resize(n+1);
    arr.resize(n+1);
    for(int i=0;i<n-1;i++)
    {
        int a,b;
        cin>>a>>b;
        adj[a].push_back(b);
        adj[b].push_back(a);
    }
    memset(dp,-1,sizeof dp);
    for(int i=1;i<=n;i++)cin>>arr[i];
    int x=min(dfs(1,0,0,1),dfs(1,0,0,0));
    if(x>=1e9)cout<<"impossible"<<endl;
    else cout<<x<<endl;
}
signed main()
{
    // freopen("meta_game_input.txt","r",stdin);
    // freopen("otput.txt","w",stdout);
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);
    preprocess();
    //bla();
    int t=1;
    //cin>>t;
    while(t--)
        solve();
}

• Subtask 1: 5 / 5
• Subtask 2: 15 / 15
• Subtask 3: 10 / 10
• Subtask 4: 40 / 40
• Subtask 5: 30 / 30