Submission #870306

#	Time	Username	Problem	Language	Result	Execution time	Memory
870306		sleepntsheep	Cat in a tree (BOI17_catinatree)	C++17	51 / 100	25 ms	5972 KiB

catinatree

#include <iostream>
#include <cstring>
#include <vector>
#include <algorithm>
#include <deque>
#include <set>
#include <utility>
#include <array>
#include <cassert>

using namespace std;
#define ALL(x) x.begin(), x.end()
#define ShinLena cin.tie(nullptr)->sync_with_stdio(false);
using i64 = long long;
#define N 200860

int n, d, l[N], h[N], alloc = 1, dp[N][2], t[N];
pair<int, int> g[N];

void upd(int p, int k) { p += 100;for (; p ; p-=p&-p) t[p] += k; }
int qry(int p) { p += 100; int z = 0; for (; p < (N<<1); p+=p&-p) z += t[p]; return z; }

void add_edge(int u, int v)
{
    g[alloc] = {v, h[u]}; h[u] = alloc++;
}

void dfs(int u, int p, int dep)
{
    l[u] = dep;
    int base = 0;

    for (auto j = h[u]; j; j = g[j].second)
    {
        int v = g[j].first;
        if (v == p) continue;
        dfs(v, u, dep+1), base += dp[v][0] - 1;
    }

    vector<int> depmap;
    for (auto j = h[u]; j; j = g[j].second)
        if (g[j].first != p) 
            upd(dp[g[j].first][1], 1), depmap.emplace_back(dp[g[j].first][1]);
    sort(ALL(depmap));

    {
        int sel = base + 1 + qry(d + dep);
        if (dp[u][0] < sel) dp[u][0] = sel, dp[u][1] = dep;
        else if (dp[u][0] == sel && dep > dp[u][1]) dp[u][1] = dep;
    }

    for (auto j = h[u]; j; j = g[j].second)
    {
        int v = g[j].first;
        if (v == p) continue;
        int delta = dp[v][1] - dep;
        int safe = (d+1)/2, sel;
        int subdep = dp[v][1];
        if (delta >= safe)
        {
            sel = base + qry(dep + safe);
            auto it = lower_bound(ALL(depmap), dep+safe);
            subdep = *it;
        }
        else
        {
            assert(max(safe, d-delta) > delta);
            upd(dp[g[j].first][1], -1);
            sel = base + 1 + qry(dep + max(safe, d - delta));
            upd(dp[g[j].first][1], 1);
        }
        if (dp[u][0] < sel) dp[u][0] = sel, dp[u][1] = subdep;
        else if (dp[u][0] == sel && subdep > dp[u][1]) dp[u][1] = subdep;
    }

    for (auto j = h[u]; j; j = g[j].second)
        if (g[j].first != p) upd(dp[g[j].first][1], -1);
}

int main()
{
    ShinLena;
    cin >> n >> d;
    for (int i = 1, v; i < n; ++i) cin >> v, add_edge(v, i);
    dfs(0, 0, 1);
    for (int i = 0; i < n; ++i)
    {
    //    cerr << dp[i][0] << ' '<< dp[i][1] << ' ' <<l[i] <<endl;
    }
    cout << dp[0][0];

    return 0;
}

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