Submission #590300

#	Time	Username	Problem	Language	Result	Execution time	Memory
590300		Lobo	The Xana coup (BOI21_xanadu)	C++17	100 / 100	276 ms	105924 KiB

xanadu

#include<bits/stdc++.h>
using namespace std;

const long long inf = (long long) 1e18 + 10;
const int inf1 = (int) 1e9 + 10;
#define int long long
#define dbl long double
#define endl '\n'
#define sc second
#define fr first
#define mp make_pair
#define pb push_back
#define all(x) x.begin(), x.end()

const int maxn = 1e5+10;

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

int sol(int u, int qtdtr, int tr, int id, int ant) {
    if(mark[u][qtdtr][tr][id]) return dp[u][qtdtr][tr][id];
    mark[u][qtdtr][tr][id] = 1;

    if(id == (int) g[u].size()) {
        if((qtdtr^a[u]) == 0) dp[u][qtdtr][tr][id] = 0;
        else dp[u][qtdtr][tr][id] = inf;
        // cout << u << " " << qtdtr << " " << tr << " " << id << "  " << ant << " " << dp[u][qtdtr][tr][id] << endl;
        return dp[u][qtdtr][tr][id];
    }
    int v = g[u][id];
    if(v == ant) return dp[u][qtdtr][tr][id] = sol(u,qtdtr,tr,id+1,ant);
    int ans = inf;
    dp[u][qtdtr][tr][id] = inf;

    //nao troco o v
    dp[u][qtdtr][tr][id] = min(dp[u][qtdtr][tr][id],sol(u,qtdtr,tr,id+1,ant)+sol(v,tr,0,0,u));
    //troco o v
    dp[u][qtdtr][tr][id] = min(dp[u][qtdtr][tr][id],sol(u,qtdtr^1,tr,id+1,ant)+sol(v,tr^1,1,0,u)+1);
    // cout << u << " " << qtdtr << " " << tr << " " << id << "  " << dp[u][qtdtr][tr][id] << endl;
    return dp[u][qtdtr][tr][id];
}

void solve() {
    cin >> n;
    for(int i = 1; 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++) {
        for(int j1 = 0; j1 <= 1; j1++) {
            for(int j2 = 0; j2 <= 1; j2++) {
                mark[i][j1][j2].pb({});
                dp[i][j1][j2].pb({});
                for(int k = 0; k <= (int) g[i].size()+3; k++) {
                    mark[i][j1][j2].pb(0);
                    dp[i][j1][j2].pb(0);
                }
            }
        }
    }

    int ans = min(sol(1,0,0,0,0),sol(1,1,1,0,0)+1);
    if(ans >= n+1) cout << "impossible" << endl;
    else cout << ans << endl;
}

int32_t main() {
    ios::sync_with_stdio(false); cin.tie(0);

    // freopen("in.in", "r", stdin);
    // freopen("out.out", "w", stdout);
    int tt = 1;
    // cin >> tt;
    while(tt--) {
        solve();
    }

}

Compilation message (stderr)

xanadu.cpp: In function 'long long int sol(long long int, long long int, long long int, long long int, long long int)':
xanadu.cpp:32:9: warning: unused variable 'ans' [-Wunused-variable]
   32 |     int ans = inf;
      |         ^~~

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