Submission #237356

#	Time	Username	Problem	Language	Result	Execution time	Memory
237356		IgorI	Cat in a tree (BOI17_catinatree)	C++17	100 / 100	493 ms	221944 KiB

catinatree

#include <bits/stdc++.h>

using namespace std;

typedef long long ll;

const int N = 200000;
const int K = 800;

int n, d;
int dp[N][N / K + 5];
int p[N];
vector<int> graph[N];

void dfs1(int v)
{
    for (auto u : graph[v]) dfs1(u);
    dp[v][0] = 1;
    for (auto u : graph[v]) dp[v][0] += dp[u][d - 1];
    for (int j = d; j > 0; j--)
    {
        if (2 * j >= d)
        {
            for (auto u : graph[v])
            {
                dp[v][j] += dp[u][j - 1];
            }
        }
        else
        {
            dp[v][j] = dp[v][d - j];
            int r = 0;
            for (auto u : graph[v])
            {
                r = max(r, dp[u][j - 1] - dp[u][d - j - 1]);
            }
            dp[v][j] += r;
        }
    }
    for (int j = d - 1; j >= 0; j--) dp[v][j] = max(dp[v][j], dp[v][j + 1]);
}

int max_place[N];

void dfs2(int v)
{
    for (auto u : graph[v]) dfs2(u);
    // dp[v][k] - nearest to v if placed k
    dp[v][0] = 1e9;
    vector<int> Up;
    for (auto u : graph[v])
    {
        for (int i = 1; dp[u][i] != -1; i++)
        {
            Up.push_back(min(d, dp[u][i] + 1));
        }
    }
    sort(Up.begin(), Up.end());
    reverse(Up.begin(), Up.end());
    int lka = 1e9, rka = 0;
    for (int i = 0; i < Up.size(); i++)
    {
        if (Up[i] * 2 >= d)
        {
            lka = min(lka, i + 1);
            //cout << "set " << i + 1 << " " << Up[i] << endl;
            dp[v][i + 1] = Up[i];
            rka = max(rka, i + 1);
        }
    }
    for (int i = rka - 1; i >= 0; i--) dp[v][i] = max(dp[v][i], dp[v][i + 1]);
    /*for (auto u : graph[v])
    {
        for (int i = 0; dp[u][i] != -1; i++)
        {
            int d1 = dp[u][i] + 1;
            int d2 = max(d1, d - d1);
            int L = lka - 1, R = rka;
            while (L + 1 < R)
            {
                int M = (L + R) / 2;
                if (dp[v][M] >= d2) L = M;
                else R = M;
            }
            if (L == lka - 1)
                L = 0;
            int will_have = L + i;
            for (int j = 0; dp[u][j] != 1; j++)
            {
                if (dp[u][j] >= d2)
                {
                    will_have -= j;
                    cout << "TAPOK ! " << j << endl;
                    break;
                }
            }
            dp[v][will_have] = max(dp[v][will_have], d1);
        }
    }*/

    for (auto u : graph[v])
    {
        for (int i = 1; dp[u][i] != -1; i++)
        {
            int d1 = dp[u][i] + 1;
            int d2 = max(d1, d - d1) - 1;
            int will_have = i;
            for (auto w : graph[v]) if (w != u)
            {
                for (int j = 1; dp[w][j] != -1; j++)
                {
                    if (dp[w][j] >= d2)
                    {
                        will_have++;
                    }
                }
            }
            //cout << u << " " << i << " " << d1 << " " << d2 << " " << will_have << endl;
            //cout << u << "->" << i << " " << will_have << endl;
            dp[v][will_have] = max(dp[v][will_have], d1);
        }
    }

    for (int i = 0; dp[v][i] != -1; i++)
    {
        max_place[v] = i;
        if (dp[v][i] >= d && dp[v][i + 1] == -1)
        {
            dp[v][i + 1] = 0;
        }
    }
    /*cout << v << ": ";
    for (int i = 0; dp[v][i] != -1; i++)
    {
        cout << dp[v][i] << " ";
    }
    cout << endl;*/
}

signed main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    cin >> n >> d;
    if (d == 1) cout << n, exit(0);
    for (int i = 1; i < n; i++)
    {
        cin >> p[i];
        graph[p[i]].push_back(i);
    }
    if (d < K)
    {
        dfs1(0);
        cout << dp[0][0] << endl;
    }
    else
    {
        for (int i = 0; i < N; i++) for (int j = 0; j < N / K + 5; j++) dp[i][j] = -1;
        dfs2(0);
        cout << max_place[0] << endl;
    }
}

Compilation message (stderr)

catinatree.cpp: In function 'void dfs2(int)':
catinatree.cpp:61:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int i = 0; i < Up.size(); i++)
                     ~~^~~~~~~~~~~

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