Submission #696190

#	Time	Username	Problem	Language	Result	Execution time	Memory
696190		RaulAndrei01	The Xana coup (BOI21_xanadu)	C++17	100 / 100	120 ms	19684 KiB

xanadu

#include <iostream>
#include <bits/stdc++.h>
#include <vector>

using namespace std;
using ll = long long;
const int nmax = 1e5 + 9;
const ll inf = 1e7;
vector<int> adj[nmax];
bool on[nmax];

ll dp[2][2][nmax];

void dfs (int nod = 1, int par = 0)
{
    ll temp[2][2];

    temp[0][0] = 0;
    temp[1][0] = 0;

    temp[0][1] = inf;
    temp[1][1] = inf;
    
    for (auto to : adj[nod])
    {
        if (to == par) continue;
        
        dfs (to , nod);
        ll t[2][2];
        
        t[0][0] = min(temp[0][0] + dp[0][0][to] , temp[0][1] + dp[0][1][to]);
        t[1][0] = min (temp[1][0] + dp[1][0][to] , temp[1][1] + dp[1][1][to]);
        t[0][1] = min(temp[0][1] + dp[0][0][to] , temp[0][0] + dp[0][1][to]);
        t[1][1] = min(temp[1][0] + dp[1][1][to] , temp[1][1] + dp[1][0][to]);
        
        

        for (int i = 0; i < 2; i++)
          for (int j = 0; j < 2; j++)
            temp[i][j] = t[i][j];
    }
    if (on[nod])
    {
        dp[0][0][nod] = temp[0][1];
        dp[0][1][nod] = 1 + temp[1][0];
        dp[1][0][nod] = temp[0][0];
        dp[1][1][nod] = 1 + temp[1][1];
    }
    else {
        dp[0][0][nod] = temp[0][0];
        dp[0][1][nod] = 1 + temp[1][1];
        dp[1][0][nod] = temp[0][1];
        dp[1][1][nod] = 1 + temp[1][0];
    }
 //   cout << nod << '\n';
   // cout << temp[0][0] << ' ' << temp[0][1] << ' ' << temp[1][0] << ' ' << temp[1][1] << '\n';
  //  cout << dp[0][0][nod] << ' ' << dp[0][1][nod] << ' ' << dp[1][0][nod] <<
  //  ' '<< dp[1][1][nod];
  //  cout << '\n';
}

int main ()
{
    int n; cin >> n; 
    for (int i = 1; i < n; i++)
    {
        int x, y; cin >> x >> y;
        adj[x].push_back(y);
        adj[y].push_back(x);
    }
    for (int i = 1; i <= n; i++)
    {
        cin >> on[i];
    }
    
    dfs();
    if (min(dp[0][1][1] , dp[0][0][1]) >= inf) cout << "impossible\n";
    else cout << min(dp[0][1][1] , dp[0][0][1]);
}

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