제출 #650939

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
650939		dooompy	The Xana coup (BOI21_xanadu)	C++17	100 / 100	81 ms	19976 KiB

xanadu

#include "bits/stdc++.h"

using namespace std;

void abc() {cout << endl;}
template <typename T, typename ...U> void abc(T a, U ...b) {
    cout << a << ' ', abc(b...);
}
template <typename T> void printv(T l, T r) {
    while (l != r) cout << *l << " \n"[++l == r];
}
template <typename A, typename B> istream& operator >> (istream& o, pair<A, B> &a) {
    return o >> a.first >> a.second;
}
template <typename A, typename B> ostream& operator << (ostream& o, pair<A, B> a) {
    return o << '(' << a.first << ", " << a.second << ')';
}
template <typename T> ostream& operator << (ostream& o, vector<T> a) {
    bool is = false;
    for (T i : a) {o << (is ? ' ' : '{'), is = true, o << i;}
    return o << '}';
}

#ifdef local
#define test(args...) abc("[" + string(#args) + "]", args)
#else
#define test(args...) void(0)
#endif

using ll = long long;

vector<int> adj[100005];
ll dp[100005][2][2]; // node, black/white, press
int status[100005];

ll inf = 1e9;

void dfs(int node, int par = -1) {

    if (adj[node].size() == 1 && par != -1) {
        dp[node][status[node]][0] = 0; dp[node][1 - status[node]][1] = 1;
        return;
    }

    ll temp[2][2] = {{(ll) 1e9, (ll) 1e9}, {(ll) 1e9, (ll) 1e9}};
    bool black = true, white = true;

    for (auto nxt : adj[node]) {
        if (nxt == par) continue;

        dfs(nxt, node);

        // dont press

        if (min(dp[nxt][0][0], dp[nxt][0][1]) >= inf) {
            black = false;
        }

        if (min(dp[nxt][1][0], dp[nxt][1][1]) >= inf) white = false;

        ll t1 = (temp[0][0] >= inf && temp[0][1] >= inf ? dp[nxt][0][0] : min(temp[0][0] + dp[nxt][0][0], temp[0][1] + dp[nxt][0][1]));
        ll t2 = (temp[0][0] >= inf && temp[0][1] >= inf ? dp[nxt][0][1] : min(temp[0][0] + dp[nxt][0][1], temp[0][1] + dp[nxt][0][0]));
        
        ll t3 = (temp[1][0] >= inf && temp[1][1] >= inf ? dp[nxt][1][0] : min(temp[1][0] + dp[nxt][1][0], temp[1][1] + dp[nxt][1][1]));
        ll t4 = (temp[1][0] >= inf && temp[1][1] >= inf ? dp[nxt][1][1] : min(temp[1][0] + dp[nxt][1][1], temp[1][1] + dp[nxt][1][0]));

        temp[0][0] = t1; temp[0][1] = t2; temp[1][0] = t3; temp[1][1] = t4;
    }

    if (black) {
        dp[node][status[node]][0] = temp[0][0];
        dp[node][1 - status[node]][0] = temp[0][1];
    }

    if (white) {
        dp[node][1 - status[node]][1] = temp[1][0] + 1;
        dp[node][status[node]][1] = temp[1][1] + 1;
    }

}

int main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0); cout.tie(0);
//    freopen("", "r", stdin);
//    freopen("", "w", stdout);
    int n; cin >> n;
    for (int i = 0; i < n-1; i++) {
        int a, b; cin >> a >> b;
        adj[a].push_back(b);
        adj[b].push_back(a);
    }

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

    fill(&dp[0][0][0], &dp[0][0][0] + sizeof(dp) / sizeof(dp[0][0][0]), 1e9);
    dfs(1);

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

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