Submission #872423

#	Time	Username	Problem	Language	Result	Execution time	Memory
872423		overwatch9	Regions (IOI09_regions)	C++17	55 / 100	4838 ms	115724 KiB

regions

#include <iostream>
#include <set>
#include <vector>
#include <algorithm>
#include <unordered_map>
using namespace std;
const int maxn = 2e5 + 1;
const int maxr = 500 + 1;
int visit[maxn], finish[maxn], region[maxn];
vector <int> adj[maxn];
vector <int> region_members[maxn];
int big_region_id[maxn];
vector <unordered_map <int, int>> r1r2;
int t = 0;
void dfs(int s) {
    visit[s] = t++;
    for (auto i : adj[s])
        dfs(i);
    finish[s] = t++;
}
unordered_map <int, int> dfs2(int s) {
    unordered_map <int, int> ans;
    if (big_region_id[region[s]] != -1) {
        ans[big_region_id[region[s]]] = 1;
    }
    for (auto i : adj[s]) {
        auto res = dfs2(i);
        for (auto j : res) {
            ans[j.first] += j.second;
            if (big_region_id[s] != -1)
                r1r2[big_region_id[region[s]]][j.first] += j.second;
        }
    }
    return ans;
}
int main() {
    // freopen("in.txt", "r", stdin);
    // freopen("out.txt", "w", stdout);
    int n, r, q;
    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);
    }
    fill(big_region_id, big_region_id + maxn, -1);
    int region_members_cnt = 0;
    for (int i = 1; i <= r; i++) {
        if (region_members[i].size() > 500)
            big_region_id[i] = region_members_cnt++;
    }
    r1r2.resize(region_members_cnt);

    dfs(1);
    dfs2(1);
    while (q--) {
        int r1, r2;
        cin >> r1 >> r2;
        if (region_members[r1].size() <= 500 && region_members[r2].size() <= 500) {
            int ans = 0;
            vector <int> starts(region_members[r2].size());
            for (int j = 0; j < region_members[r2].size(); j++)
                starts[j] = visit[region_members[r2][j]];
            sort(starts.begin(), starts.end());
            for (int i = 0; i < region_members[r1].size(); i++) {
                auto l = upper_bound(starts.begin(), starts.end(), visit[region_members[r1][i]]);
                auto r = upper_bound(starts.begin(), starts.end(), finish[region_members[r1][i]]);
                if (r == starts.begin())
                    continue;
                r--;
                int id1 = l - starts.begin();
                int id2 = r - starts.begin();
                ans += max(0, (id2 - id1 + 1));
            }
            cout << ans << endl;
        } else {
            int a = big_region_id[r1];
            int b = big_region_id[r2];
            cout << r1r2[a][b] << '\n';
        }
    }
}

Compilation message (stderr)

regions.cpp: In function 'int main()':
regions.cpp:66:31: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   66 |             for (int j = 0; j < region_members[r2].size(); j++)
      |                             ~~^~~~~~~~~~~~~~~~~~~~~~~~~~~
regions.cpp:69:31: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   69 |             for (int i = 0; i < region_members[r1].size(); i++) {
      |                             ~~^~~~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 15 / 15
• Subtask 2: 40 / 85