Submission #1086478

#	Time	Username	Problem	Language	Result	Execution time	Memory
1086478		0x34c	Regions (IOI09_regions)	C++17	0 / 100	105 ms	32848 KiB

regions

#include <bits/stdc++.h>
#define ll long long
#define pii pair<int, int>
#define endl '\n'

using namespace std;

int N, R, Q, SQRT_N;
const int MAX_N = 2e5 + 1;
const int MX_SQRT = 448;
const int MAX_R = 25001;
vector<int> graph[MAX_N], rgraph[MAX_N];
int sol[MX_SQRT][MAX_R];
int regions[MAX_N], reg_cnt[MAX_R], conv[MAX_R], tin[MAX_N], tout[MAX_N], cnt[MAX_R];
vector<int> sqrt_r;

void dfs(int v)
{
    for (int r : sqrt_r)
        sol[conv[r]][regions[v]] += cnt[conv[r]];
    cnt[regions[v]]++;

    for (int u : graph[v])
        dfs(u);
    cnt[regions[v]]--;
}

void etour(int v, int &tim)
{
    rgraph[regions[v]].push_back(v);
    tin[v] = tim++;
    for (int u : graph[v])
        etour(u, tim);
    tout[v] = tim++;
}

signed main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);

    cin >> N >> R >> Q;
    SQRT_N = sqrt(N);

    cin >> regions[0];
    --regions[0];
    reg_cnt[regions[0]]++;
    for (int i = 1; i < N; i++)
    {
        int v;
        cin >> v >> regions[i];
        --regions[i];
        --v;
        graph[v].push_back(i);
        reg_cnt[regions[i]]++;
    }

    for (int i = 0; i < R; i++)
    {
        if (reg_cnt[i] >= SQRT_N)
        {
            sqrt_r.push_back(i);
            conv[i] = sqrt_r.size() - 1;
        }
        else
            conv[i] = -1;
    }

    int tim = 0;
    etour(0, tim);
    dfs(0);

    for (int _ = 0; _ < Q; _++)
    {
        int a, b;
        cin >> a >> b;
        --a;
        --b;

        if (conv[a] != -1)
        {
            cout << sol[conv[a]][b] << endl;
            continue;
        }

        int res = 0;
        for (int v : rgraph[a])
        {
            if (rgraph[b].empty())
                continue;
            int l = 0, r = rgraph[b].size() - 1;
            int lb = -1;

            int amt = 0;
            while (l <= r)
            {
                int m = l + (r - l) / 2;
                int u = rgraph[b][m];
                if (tin[u] < tin[v])
                    l = m + 1;
                else if (tout[u] > tout[v])
                    r = m - 1;
                else
                {
                    lb = m;
                    r = m - 1;
                }
            }

            if (lb == -1)
                continue;
            l = 0;
            r = rgraph[b].size() - 1;
            int rb = -1;
            amt = 0;
            while (l <= r)
            {
                int m = l + (r - l) / 2;
                int u = rgraph[b][m];
                if (tin[u] < tin[v])
                    l = m + 1;
                else if (tout[u] > tout[v])
                    r = m - 1;
                else
                {
                    rb = m;
                    l = m + 1;
                }
            }

            res += (rb - lb + 1);
        }
        cout << res << endl;
    }
}

Compilation message (stderr)

regions.cpp: In function 'int main()':
regions.cpp:94:17: warning: variable 'amt' set but not used [-Wunused-but-set-variable]
   94 |             int amt = 0;
      |                 ^~~

• Subtask 1: 0 / 15
• Subtask 2: 0 / 85