Submission #696921

#	Time	Username	Problem	Language	Result	Execution time	Memory
696921		Tien_Noob	The Xana coup (BOI21_xanadu)	C++17	100 / 100	68 ms	23172 KiB

xanadu

//Make CSP great again
//Vengeance
#include <bits/stdc++.h>
#define TASK "TESTCODE"
using namespace std;
const int N = 1e5;
int dp[N + 1][2][2];
vector<int> adj[N + 1];
int a[N + 1], n;
void read()
{
    cin >> n;
    for (int i = 1; i < n; ++i)
    {
        int u, v;
        cin >> u >> v;
        adj[u].push_back(v);
        adj[v].push_back(u);
    }
    for (int i = 1; i <= n; ++ i)
    {
        cin >> a[i];
    }
}
void DFS(int u, int p)
{
    memset(dp[u], 0x3f, sizeof(dp[u]));
    dp[u][a[u]][0] = 0;
    dp[u][1 ^ a[u]][1] = 1;
    for (int v : adj[u])
    {
        if (v == p)
        {
            continue;
        }
        DFS(v, u);
        int nw[2][2];
        memset(nw, 0x3f, sizeof(nw));
        for (int i1 = 0; i1 < 2; ++ i1)
        {
            for (int j1 = 0; j1 < 2; ++j1)
            {
                for (int i2 = 0; i2 < 2; ++ i2)
                {
                    for (int j2 = 0; j2 < 2; ++ j2)
                    {
                        int t = j1 ^ j2;
                        if (i2 ^ j1)
                        {
                            continue;
                        }
                        nw[i1 ^ j2][j1] = min(nw[i1 ^ j2][j1], dp[u][i1][j1] + dp[v][i2][j2]);
                    }
                }
            }
        }
        for (int i1 = 0; i1 < 2; ++ i1)
        {
            for (int j1 = 0; j1 < 2; ++ j1)
            {
                dp[u][i1][j1] = nw[i1][j1];
            }
        }
    }
    /*cerr << u << '\n';
    for (int i1 = 0; i1 < 2; ++ i1)
    {
        for (int j1 = 0; j1 < 2; ++ j1)
        {
            cerr << dp[u][i1][j1] << ' ';
        }
    }
    cerr << '\n';*/
}
void solve()
{
    DFS(1, 0);
    int res = min(dp[1][0][0], dp[1][0][1]);
    if (res <= n)
    {
        cout << res;
        return ;
    }
    cout << "impossible";
}
int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    if (fopen(TASK".INP", "r"))
    {
        freopen(TASK".INP", "r", stdin);
        //freopen(TASK".OUT", "w", stdout);
    }
    int t = 1;
    bool typetest = false;
    if (typetest)
    {
        cin >> t;
    }
    for (int __ = 1; __ <= t; ++ __)
    {
        //cout << "Case " << __ << ": ";
        read();
        solve();
    }
}

Compilation message (stderr)

xanadu.cpp: In function 'void DFS(int, int)':
xanadu.cpp:47:29: warning: unused variable 't' [-Wunused-variable]
   47 |                         int t = j1 ^ j2;
      |                             ^
xanadu.cpp: In function 'int main()':
xanadu.cpp:92:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   92 |         freopen(TASK".INP", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~

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