Submission #1058696

#	Time	Username	Problem	Language	Result	Execution time	Memory
1058696		gyg	Cat in a tree (BOI17_catinatree)	C++17	0 / 100	0 ms	348 KiB

catinatree

#include <bits/stdc++.h>
using namespace std;
using pii = pair<int, int>;
const int MAX_N = 18 + 5, INF = 1e9;

int n, k;
array<vector<int>, MAX_N> adj;

array<array<int, MAX_N>, MAX_N> dist;
void precomp() {
    for (int u = 1; u <= n; u++) {
        fill(dist[u].begin(), dist[u].end(), INF);
        for (int v : adj[u]) dist[u][v] = 1;
        dist[u][u] = 0;
    }

    for (int u = 1; u <= n; u++) 
        for (int v = 1; v <= n; v++) 
            for (int w = 1; w <= n; w++) 
                dist[u][v] = min(dist[u][v], dist[u][w] + dist[w][v]);
}

int query(int u) {
    int score = 0;
    for (int v = 1; v <= n; v++)
        score += (dist[u][v] < k);
    return score;
}

vector<pii> order;
array<bool, MAX_N> used;
void dfs(int u, int d = 0) {
    used[u] = true;
    if (d == k - 1) return;
    for (int v : adj[u])
        if (!used[v]) dfs(v, d + 1);
}
int comp() {
    for (int u = 1; u <= n; u++) order.push_back({query(u), u});
    sort(order.begin(), order.end());    
    
    int ans = 0;
    for (pii x : order) {
        int u = x.second;
        if (used[u]) continue;
        ans++, dfs(u);
    }
    return ans;
}

int main() {
    // freopen("cat.in", "r", stdin);
    cin >> n >> k; assert(n <= 18);
    for (int u = 2; u <= n; u++) {
        int v; cin >> v; v++;
        adj[u].push_back(v), adj[v].push_back(u);
    }

    precomp();
    int ans = comp();
    cout << ans << '\n';
}

• Subtask 1: 0 / 11
• Subtask 2: 0 / 40
• Subtask 3: 0 / 49