Submission #602016

#	Time	Username	Problem	Language	Result	Execution time	Memory
602016		SOCIOPATE	The Xana coup (BOI21_xanadu)	C++17	100 / 100	124 ms	39644 KiB

xanadu

#ifdef LOCAL
    #define _GLIBCXX_DEBUG
#endif

#include <bits/stdc++.h>

#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

using namespace std;
using namespace __gnu_pbds;

typedef long long ll;
typedef long double ld;
typedef unsigned long long ull;

#define pll pair<ll, ll>
#define pii pair<int, int>
#define pdd pair<ld, ld>
#define ff first
#define ss second
#define all(v) v.begin(),v.end()

typedef tree<
    int,
    null_type,
    less<int>,
    rb_tree_tag,
    tree_order_statistics_node_update> ordset;

#pragma GCC optimize("-O3")
#pragma GCC optimize("unroll-loops")
#pragma GCC optimize("-Os")

ll INF = 1000000000;
ll mod = 1e9 + 7;

mt19937 gen(time(0));

vector<vector<int>> a;
vector<vector<vector<ll>>> dp; // the first parametr is a vertex, the second is 1 if vertex turned on and the third is 1 if we toggle vertex
vector<int> is;

void dfs(int v, int p){
    if(a[v].size() == 1 && p != -1) {
        if(is[v]){
            dp[v][1][0] = 0;
            dp[v][0][1] = 1;
        }
        else{
            dp[v][0][0] = 0;
            dp[v][1][1] = 1;
        }
        return;
    }
    int i = 0;
    for(int u : a[v]){
        if(u == p){
            swap(a[v][i], a[v].back());
        }
        i++;
    }
    if(p != -1) a[v].pop_back();
    for(int u : a[v]){
        dfs(u, v);
    }
    vector<vector<ll>> dp2((int)a[v].size(), vector<ll>(2, INF)), dp22((int)a[v].size(), vector<ll>(2, INF));
    for(int i = 0; i < (int)a[v].size(); i++){
        if(a[v][i] == p) continue;
        if(!i) {
            dp2[i][0] = dp[a[v][i]][1][0];
            dp2[i][1] = dp[a[v][i]][1][1];
            dp22[i][0] = dp[a[v][i]][0][0];
            dp22[i][1] = dp[a[v][i]][0][1];
        } else {
            dp2[i][0] = min(dp2[i - 1][0] + dp[a[v][i]][1][0], dp2[i - 1][1] + dp[a[v][i]][1][1]);
            dp2[i][1] = min(dp2[i - 1][1] + dp[a[v][i]][1][0], dp2[i - 1][0] + dp[a[v][i]][1][1]);
            dp22[i][0] = min(dp22[i - 1][0] + dp[a[v][i]][0][0], dp22[i - 1][1] + dp[a[v][i]][0][1]);
            dp22[i][1] = min(dp22[i - 1][1] + dp[a[v][i]][0][0], dp22[i - 1][0] + dp[a[v][i]][0][1]);
        }
    }
    if(!is[v]){
        dp[v][0][0] = dp22[(int)a[v].size() - 1][0];
        dp[v][1][1] = dp2[(int)a[v].size() - 1][0] + 1ll;
        dp[v][0][1] = dp2[(int)a[v].size() - 1][1] + 1ll;
        dp[v][1][0] = dp22[(int)a[v].size() - 1][1];
    } else{
        dp[v][0][0] = dp22[(int)a[v].size() - 1][1];
        dp[v][1][1] = dp2[(int)a[v].size() - 1][1] + 1ll;
        dp[v][0][1] = dp2[(int)a[v].size() - 1][0] + 1ll;
        dp[v][1][0] = dp22[(int)a[v].size() - 1][0];
    }
}

void solve(){
    int n;
    cin >> n;
    a.resize(n);
    dp.resize(n, vector<vector<ll>>(2, vector<ll>(2, INF)));
    is.resize(n);
    for(int i = 0; i < n - 1; i++){
        int u, v;
        cin >> u >> v;
        u--; v--;
        a[u].push_back(v);
        a[v].push_back(u);
    }
    for(int i = 0; i < n; i++) cin >> is[i];
    if(n == 1){
        cout << is[0];
        return;
    }
    dfs(0, -1);
    if(min(dp[0][0][0], dp[0][0][1]) >= INF){
        cout << "impossible";
    } else cout << min(dp[0][0][0], dp[0][0][1]);
}

int main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    #ifdef LOCAL
        freopen("input.txt", "r", stdin);
    #endif
	int tt;
    //cin >> tt;
	tt = 1;
	while (tt--) {
		solve();
		#ifdef LOCAL
            cout << "__________________________________" << endl;
		#endif
	}
	#ifdef LOCAL
        cout << "finished in " << clock() * 1.0 / CLOCKS_PER_SEC << "sec" << '\n';
	#endif
	return 0;
}

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