Submission #668932

#	Time	Username	Problem	Language	Result	Execution time	Memory
668932		mychecksedad	The Xana coup (BOI21_xanadu)	C++17	55 / 100	86 ms	21596 KiB

xanadu

/* Author : Mychecksdead */
#include<bits/stdc++.h>
using namespace std;
typedef long long int ll;
#define pb push_back
const int N = 1e5 + 5;

int n, dp[N][2][2], a[N];
vector<int> g[N];

void dfs(int v, int p){
    bool ok = 1;
    vector<int> c;
    for(int u: g[v]){
        if(u == p) continue;
        dfs(u, v);
        ok = 0;
        c.pb(u);
    }
    int s = c.size();
    for(int mask = 0; mask < (1<<s); ++mask){
        int k = __builtin_popcount(mask);
        k = k % 2;
        int x = 0, y = 0;
        for(int j = 0; j < s; ++j){
            int child = c[j];
            if((1<<j)&mask){
                x += dp[child][1][0];
                y += dp[child][1][1];
            }else{
                x += dp[child][0][0];
                y += dp[child][0][1];
            }
        }
        dp[v][0][a[v]^k] = min(dp[v][0][a[v]^k], x);
        dp[v][1][a[v]^k^1] = min(dp[v][1][a[v]^k^1], y + 1);
    }
}

void solve(){
    cin >> n;
    for(int i = 0; i < n - 1; ++i){
        int u, v; cin >> u >> v;
        g[u].pb(v);
        g[v].pb(u);
    }

    for(int i = 1; i <= n; ++i) cin >> a[i];

    for(int i = 1; i <= n; ++i) dp[i][0][0] = dp[i][0][1] = dp[i][1][0] = dp[i][1][1] = N;

    dfs(1, 0);

    if(min(dp[1][0][0], dp[1][1][0]) >= N){
        cout << "impossible";
    }else{
        cout << min(dp[1][0][0], dp[1][1][0]);
    }
}




int main(){
    cin.tie(0); ios::sync_with_stdio(0);
    solve();
    return 0;
 
}

Compilation message (stderr)

xanadu.cpp: In function 'void dfs(int, int)':
xanadu.cpp:12:10: warning: variable 'ok' set but not used [-Wunused-but-set-variable]
   12 |     bool ok = 1;
      |          ^~

• Subtask 1: 5 / 5
• Subtask 2: 0 / 15
• Subtask 3: 10 / 10
• Subtask 4: 40 / 40
• Subtask 5: 0 / 30