제출 #1058722

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
1058722		gyg	Cat in a tree (BOI17_catinatree)	C++17	11 / 100	1067 ms	9564 KiB

catinatree

#include <bits/stdc++.h>
using namespace std;
using pii = pair<int, int>;
const int MAX_N = 1500 + 5, INF = 1e9;

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

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

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


array<int, MAX_N> siz;
array<bool, MAX_N> del;
void update_siz(int u, int par = -1) {
    siz[u] = 1;
    for (int v : adj[u]) {
        if (v == par) continue;
        if (del[v]) continue;
        update_siz(v, u), siz[u] += siz[v];
    }
}
int find_cent(int u, int tot_siz, int par = -1) {
    for (int v : adj[u]) {
        if (v == par) continue;
        if (del[v]) continue;
        if (siz[v] * 2 > tot_siz) return find_cent(v, tot_siz, u);
    }
    return u;
}

array<vector<int>, MAX_N> ancs; // Reversed
array<unordered_map<int, int>, MAX_N> dist;
array<unordered_map<int, vector<pii>>, MAX_N> dists; // [itself] = whole thing
void find_dists(int u, int d, int par, int cent, int sub) {
    dist[cent][u] = d, dists[cent][sub].push_back({d, u});
    ancs[u].push_back(cent);
    for (int v : adj[u]) {
        if (v == par) continue;
        if (del[v]) continue;
        find_dists(v, d + 1, u, cent, sub);
    }
}

void build(int u = 1) {
    update_siz(u);
    int cent = find_cent(u, siz[u]);

    dist[cent][cent] = 0, dists[cent][cent].push_back({0, cent});
    ancs[cent].push_back(cent);
    for (int v : adj[cent]) {
        if (del[v]) continue;
        find_dists(v, 1, u, cent, v);
        sort(dists[cent][v].begin(), dists[cent][v].end());
        dists[cent][cent].insert(dists[cent][cent].begin(), dists[cent][v].begin(), dists[cent][v].end());
    }
    sort(dists[cent][cent].begin(), dists[cent][cent].end());

    del[cent] = true;
    for (int v : adj[cent])
        if (!del[v]) build(v);
}

int mini_query(int u, int d, int exc) {
    int i = lower_bound(dists[u][u].begin(), dists[u][u].end(), make_pair(d, -1)) - 1 - dists[u][u].begin(); // First index with dist < d
    int j = (exc == -1) ? -1 : lower_bound(dists[u][exc].begin(), dists[u][exc].end(), make_pair(d, -1)) - 1 - dists[u][exc].begin();
    int ans = i + 1 - (j + 1);
    return ans;
}
int query(int u) {
    // reverse(ancs[u].begin(), ancs[u].end());
    // int ans = 0;
    // for (int i = 0; i < ancs[u].size(); i++) {
    //     int v = ancs[u][i];
    //     if (i == 0) ans += mini_query(v, k, -1);
    //     else ans += mini_query(v, k - dist[v][u], ancs[u][i - 1]);
    // }
    // cout << u << ": " << ans << endl;
    // return ans;
    int score = 0;
    for (int v = 1; v <= n; v++)
        score += (floyd[u][v] < k);
    return score;
}

vector<pii> order;
array<bool, MAX_N> used;
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++;
        for (int v = 1; v <= n; v++)
            if (floyd[u][v] < k) used[v] = true;
    }
    return ans;
}

int main() {
    // freopen("cat.in", "r", stdin);
    cin >> n >> k; assert(n <= 1500);
    for (int u = 2; u <= n; u++) {
        int v; cin >> v; v++;
        adj[u].push_back(v), adj[v].push_back(u);
    }

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

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