Submission #1190658

#	Time	Username	Problem	Language	Result	Execution time	Memory
1190658		DanielPr8	The Xana coup (BOI21_xanadu)	C++20	100 / 100	51 ms	30792 KiB

xanadu

#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using vll = vector<ll>;
using vvl = vector<vll>;
using pll = pair<ll,ll>;
using vpl = vector<pll>;
using vvp = vector<vpl>;

#define f first
#define s second
#define pb push_back
#define all(v) v.begin(),v.end()
vvl g, dp;
vll st;
ll calc(vll& up, bool x){
    ll ans = 0;
    if(!x){
        for(ll i = 1; i < up.size(); i+=2){
            ans += min<ll>(0, up[i]+up[i-1]);
        }
    }
    else{
        if(up.empty())return 1e9;
        ans+=up[0];
        for(ll i = 2; i < up.size(); i+=2){
            ans += min<ll>(0, up[i]+up[i-1]);
        }
    }
    return ans;
}
void dfs(ll cur, ll par){
    vll up0, up1;
    for(ll i:g[cur]){
        if(i==par)continue;
        dfs(i, cur);
        dp[cur][0]+=dp[i][0];
        dp[cur][2]+=dp[i][0];
        up0.pb(dp[i][1] - dp[i][0]);
        dp[cur][1]+=dp[i][2];
        dp[cur][3]+=dp[i][2];
        up1.pb(dp[i][3] - dp[i][2]);
    }
    sort(all(up0));
    sort(all(up1));
    dp[cur][1]++;
    dp[cur][3]++;
    if(st[cur]==0){
        dp[cur][0] += calc(up0, 0);
        dp[cur][2] += calc(up0, 1);
        dp[cur][1] += calc(up1, 1);
        dp[cur][3] += calc(up1, 0);
    }
    else{
        dp[cur][0] += calc(up0, 1);
        dp[cur][2] += calc(up0, 0);
        dp[cur][1] += calc(up1, 0);
        dp[cur][3] += calc(up1, 1);
    }
}
int main(){
    ios_base::sync_with_stdio(0);cin.tie(NULL);
    ll n, a, b;
    cin >> n;
    g = vvl(n);
    dp = vvl(n, vll(4));
    st=vll(n);
    for(ll i = 0; i < n-1; ++i){
        cin >> a >> b;
        a--;b--;
        g[a].pb(b);
        g[b].pb(a);
    }
    for(ll i = 0; i < n; ++i)cin >> st[i];
    dfs(0,0);
    ll ans = min(dp[0][0], dp[0][1]);
    if(ans > n)cout << "impossible";
    else cout << ans;
}

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