Submission #447249

#	Time	Username	Problem	Language	Result	Execution time	Memory
447249		ak2006	The Xana coup (BOI21_xanadu)	C++14	100 / 100	168 ms	39932 KiB

xanadu

#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using vb = vector<bool>;
using vvb = vector<vb>;
using vi = vector<int>;
using vvi = vector<vi>;
using vl = vector<ll>;
using vvl = vector<vl>;
using vvvl = vector<vvl>;
const ll mod = 1e9 + 7,inf = 1e18;
#define pb push_back
#define fast ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
void setIO()
{
    fast;
}
int n = 1e5 + 5;
vvi adj(n);
vvvl dp(n,vvl(2,vl(2,1e9)));
vl vals(n);
void dfs(int u,int p)
{
    dp[u][vals[u]][0] = dp[u][vals[u]][1] = 0;
    for (int v:adj[u]){
        if (v == p)continue;
        dfs(v,u);
        vvl temp(4,vl(4));
        for (int f1 = 0;f1<2;f1++){
            for (int f2 = 0;f2<2;f2++){
                temp[f1][f2] = min(
                    dp[u][f1][f2] + dp[v][f2][0],
                    dp[u][!f1][f2] + dp[v][!f2][1] + 1
                    );
            }
        }
        for (int f1 = 0;f1<2;f1++)for (int f2 = 0;f2<2;f2++)dp[u][f1][f2] = temp[f1][f2];
    }
}
int main()
{
    setIO();
    cin>>n;
    for (int i = 1;i<=n - 1;i++){
        int u,v;
        cin>>u>>v;
        adj[u].pb(v),adj[v].pb(u);
    }
    for (int i = 1;i<=n;i++)cin>>vals[i];
    dfs(1,0);
    ll ans = min(dp[1][0][0],dp[1][1][1] + 1);
    if (ans > n)cout<<"impossible";
    else cout<<ans;
    return 0;
}

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