Submission #1032546

#	Time	Username	Problem	Language	Result	Execution time	Memory
1032546		HorizonWest	The Xana coup (BOI21_xanadu)	C++17	100 / 100	58 ms	19796 KiB

xanadu

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

#pragma GCC optimize("O3")
#define endl '\n'
#define db double
#define ll __int128
#define int long long
#define pb push_back
#define fs first
#define sd second
#define Mod long(1e9 + 7)
#define all(x) x.begin(), x.end()
#define unvisited long(-1)
#define Eps double(1e-9)
#define _for(i, n) for(int i = 0; i < (n); i++)
#define dbg(x) cout << #x ": " << x << endl;

const int Max = 1e6 + 7, Inf = 1e9 + 7;

void print(bool x) { cout << (x ? "YES" : "NO") << endl; }

string tostring (__int128 x)
{
    string ans = "";
    while(x > 0)
    {
        ans += (x % 10 + '0');
        x /= 10;
    }
    reverse(all(ans));
    return ans;
}

vector <vector<int>> v, dp; 
vector <int> a; 

void dfs(int node, int parent)
{
    dp[node][a[node]] = 0;
    dp[node][(a[node] ^ 1) + 2] = 1;

    for(auto& u : v[node]) if(u != parent)
    {
        dfs(u, node); 
        vector <int> dp1(4, Inf); 

        dp1[0] = min(dp[u][0] + dp[node][0], dp[u][2] + dp[node][1]); 
        dp1[1] = min(dp[u][2] + dp[node][0], dp[u][0] + dp[node][1]); 
        dp1[2] = min(dp[u][3] + dp[node][3], dp[u][1] + dp[node][2]); 
        dp1[3] = min(dp[u][3] + dp[node][2], dp[u][1] + dp[node][3]); 

        swap(dp1, dp[node]); 
    }
}

void solve()
{
    int n; cin >> n;

    a.assign(n+1, 0);
    v.assign(n+1, vector <int> ()); 
    dp.assign(n+1, vector <int> (4, Inf)); 

    _for(i, n-1){
        int a, b; cin >> a >> b; 
        v[a].pb(b); v[b].pb(a); 
    }

    _for(i, n) cin >> a[i+1]; 

    dfs(1, 0); 

    int ans = min(dp[1][0], dp[1][2]);

    if(ans >= Inf)
        cout << "impossible" << endl; 
    else 
        cout << ans << endl; 
}

int32_t main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);

    int Q = 1; //cin >> Q;

    while (Q--)
    {
        solve();
    }

    return 0;
}

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