Submission #872519

#	Time	Username	Problem	Language	Result	Execution time	Memory
872519		overwatch9	Regions (IOI09_regions)	C++17	100 / 100	3982 ms	66764 KiB

regions

#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
const int maxn = 2e5 + 10;
const int maxr = 25000 + 10;
vector <int> adj[maxn];
int region[maxn];
vector <int> region_members[maxr];
int visit[maxn], finish[maxn];
int n, r, q, t = 0;
void dfs(int s) {
    visit[s] = t++;
    for (auto i : adj[s])
        dfs(i);
    finish[s] = t++;
}
vector <vector <int>> r1r2, cnt;
int big_region_cnt = 0;
int big_id[maxn];
void dfs2(int s, int p) {
    int id1 = big_id[region[s]];
    int id2 = big_id[region[p]];
    cnt[s] = cnt[p];
    if (id2 != -1 && s != p)
        cnt[s][id2]++;
    if (id1 != -1) {
        for (int i = 0; i < big_region_cnt; i++)
            r1r2[i][id1] += cnt[s][i];
    }
    for (auto i : adj[s])
        dfs2(i, s);
}
int main() {
    // freopen("in.txt", "r", stdin);
    // freopen("out.txt", "w", stdout);
    cin >> n >> r >> q;
    cin >> region[1];
    region_members[region[1]].push_back(1);
    for (int i = 2; i <= n; i++) {
        int x;
        cin >> x;
        adj[x].push_back(i);
        cin >> region[i];
        region_members[region[i]].push_back(i);
    }
    dfs(1);
    vector <vector <int>> starts(r+1);
    for (int i = 1; i <= r; i++) {
        for (auto j : region_members[i])
            starts[i].push_back(visit[j]);
        sort(starts[i].begin(), starts[i].end());
    }
    fill(big_id, big_id + maxn, -1);
    for (int i = 1; i <= r; i++) {
        if (region_members[i].size() > 500)
            big_id[i] = big_region_cnt++;
    }

    r1r2 = vector <vector <int>> (big_region_cnt + 10, vector <int> (big_region_cnt + 10));
    cnt = vector <vector <int>> (n+1, vector <int> (big_region_cnt + 10));
    dfs2(1, 1);

    while (q--) {
        int r1, r2;
        cin >> r1 >> r2;
        if (region_members[r1].size() <= 500) { // small
            int ans = 0;
            for (auto i : region_members[r1]) {
                auto l = upper_bound(starts[r2].begin(), starts[r2].end(), visit[i]) - starts[r2].begin();
                auto r = upper_bound(starts[r2].begin(), starts[r2].end(), finish[i]) - starts[r2].begin();
                ans += max(0, (int)(r - l));
            }
            cout << ans << endl;
        } else if (region_members[r2].size() <= 500) { // small
            int ans = 0;
            for (auto i : region_members[r2]) {
                ans += cnt[i][big_id[r1]];
            }
            cout << ans << endl;
        } else {
            cout << r1r2[big_id[r1]][big_id[r2]] << endl;
        }
    }

}

• Subtask 1: 15 / 15
• Subtask 2: 85 / 85