제출 #1156274

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
1156274		mmdrzada	Star Trek (CEOI20_startrek)	C++20	8 / 100	1096 ms	328 KiB

startrek

#include <bits/stdc++.h>

#define int long long
using namespace std;


#define fastIO ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
#define pb push_back
#define pii pair<int, int>
#define S second
#define F first
#define sep ' '
#define vi vector<int>
#define mid (l+r)/2
#define pbb pair<bool, bool>
#define trint array<int, 3>
const int N = 1e3+10, M = 1e9+7;
int n, d;
vi adj[N];
int exi, stat;
int cnt[2][2];

bool dfs(int v, int p = -1) {
    if (v == exi && stat == false) return true;
    for(int neigh: adj[v]) {
        if (neigh == p) continue;
        if (dfs(neigh, v) == false) return true;
    }
    return false;
}

void solve() {
    cin >> n >> d;
    assert(n <= 1e3 && d <= 1e5);
    for(int i = 0 ; i < n-1 ; i ++) {
        int u, v; cin >> u >> v;u --, v --; adj[u].pb(v), adj[v].pb(u);
    }
    for(int root = 0 ; root < n ; root ++) {
        for(exi = 0; exi < n ; exi ++) {
            for(stat = 0; stat <= 1; stat++) {
                bool res = dfs(root);
                cnt[res][stat]++;
            }
        }
    }
    // cout << "#\n";
    exi = -1;
    vi base(2);
    for(int root = 0 ; root < n ; root ++) {
        base[dfs(root)]++;
    }
    for(int i = 1 ; i <= d-1 ; i ++) {
        base = {
            (1ll * base[0] * cnt[0][0] % M + 1ll * base[1] * cnt[0][1] % M) % M,
            (1ll * base[0] * cnt[1][0] % M + 1ll * base[1] * cnt[1][1] % M) % M,
        };
    }
    int ans = 0;
    for(exi = 0; exi < n ; exi ++) {
        for(stat = 0; stat <= 1; stat++) {
            if (dfs(0)) {
                ans += base[stat];
                ans %= M;
            }
        }
    }
    cout << ans << endl;
}

int32_t main() {
    fastIO;

    solve();

    return 0; 
}

• Subtask 1: 0 / 0
• Subtask 2: 0 / 7
• Subtask 3: 8 / 8
• Subtask 4: 0 / 15
• Subtask 5: 0 / 15
• Subtask 6: 0 / 20
• Subtask 7: 0 / 20
• Subtask 8: 0 / 15