Submission #1307143

#	Time	Username	Problem	Language	Result	Execution time	Memory
1307143		DangKhoizzzz	The Xana coup (BOI21_xanadu)	C++20	100 / 100	45 ms	22356 KiB

xanadu

#include <bits/stdc++.h>
#define int long long
#define fi first
#define se second
#define pii pair <int , int>
#define arr3 array <int , 3>

using namespace std;

const int INF = 1e18;
const int maxn = 120003;
const int mod = 998244353;

int n , f[maxn][2][2] , val[maxn];
vector <int> g[maxn];

void chmin(int &a , int b) {a = min(a , b);}

// dinh u / chon hoac ko chon / gia tri dinh

void dfs(int u , int p)
{
    for(int x = 0; x < 2; x++)
    {
        for(int y = 0; y < 2; y++) f[u][x][y] = INF;
    }
    f[u][0][val[u]] = 0;
    f[u][1][val[u]^1] = 1;

    for(int v: g[u])
    {
        if(v == p) continue;
        dfs(v , u);
        int dp[2][2];
        for(int x = 0; x < 2; x++)
        {
            for(int y = 0; y < 2; y++)
            {
                dp[x][y] = f[u][x][y];
                f[u][x][y] = INF;
            }
        }
        for(int a = 0; a < 2; a++)
        {
            for(int b = 0; b < 2; b++)
            {
                for(int x = 0; x < 2; x++)
                {
                    for(int y = 0; y < 2; y++)
                    {
                        if((y^a) == 0) chmin(f[u][a][b^x] , dp[a][b] + f[v][x][y]);
                    }
                }
            }
        }
    }
}

void solve()
{
    cin >> n;
    for(int i = 1; i < n; i++)
    {
        int u , v; cin >> u >> v;
        g[u].push_back(v);
        g[v].push_back(u);
    }
    for(int i = 1; i <= n; i++) cin >> val[i];
    dfs(1 , 1);
    int ans = min(f[1][0][0] , f[1][1][0]);
    if(ans == INF) cout << "impossible" << '\n';
    else cout << ans << '\n';
}

signed main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(0); cout.tie(0);
    //freopen("inp.txt", "r", stdin); freopen("out.txt", "w", stdout);
    solve();
    return 0;
}

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