Submission #750599

#	Time	Username	Problem	Language	Result	Execution time	Memory
750599		Kihihihi	Cat Exercise (JOI23_ho_t4)	C++17	100 / 100	536 ms	82088 KiB

Main

#include <iostream>
#include <iomanip>
#include <algorithm>
#include <numeric>
#include <cmath>
#include <cassert>
#include <ctime>
#include <chrono>
#include <cstdio>
#include <random>
#include <vector>
#include <string>
#include <map>
#include <unordered_map>
#include <set>
#include <unordered_set>
#include <deque>
#include <queue>
#include <bitset>
#include <list>
#include <fstream>
#include <functional>
#include <complex>
using namespace std;
mt19937_64 rnd(chrono::steady_clock::now().time_since_epoch().count());

short skip_cin = 0;
const long long INF = 1e18, MOD = 1e9 + 7, MOD2 = 998244353, LOG = 19;
const long double EPS = 1e-9, PI = acos(-1);

struct dsu
{
    long long n;
    vector<long long> p, rk, mx;

    dsu(long long in, vector<long long>& val)
    {
        n = in;
        p.resize(n);
        iota(p.begin(), p.end(), 0);
        rk.resize(n);
        mx = val;
    }

    long long rt(long long v)
    {
        return (p[v] == v ? v : p[v] = rt(p[v]));
    }

    void unite(long long a, long long b)
    {
        a = rt(a);
        b = rt(b);
        if (a == b)
        {
            return;
        }

        if (rk[a] < rk[b])
        {
            swap(a, b);
        }
        mx[a] = max(mx[a], mx[b]);
        p[b] = a;
        rk[a] += (rk[a] == rk[b]);
    }
};

long long n;
vector<long long> g[200000];
vector<long long> val, pos;
vector<long long> binup[200000];
vector<long long> h;

void build_binup(long long v, long long p)
{
    h[v] = (p == -1 ? 0 : h[p] + 1);
    binup[v][0] = (p == -1 ? v : p);
    for (long long i = 1; i < LOG; i++)
    {
        binup[v][i] = binup[binup[v][i - 1]][i - 1];
    }

    for (auto& i : g[v])
    {
        if (i == p)
        {
            continue;
        }

        build_binup(i, v);
    }
}

long long get_la(long long v, long long x)
{
    for (long long i = LOG - 1; i > -1; i--)
    {
        if (h[v] - h[binup[v][i]] <= x)
        {
            x -= h[v] - h[binup[v][i]];
            v = binup[v][i];
        }
    }
    return v;
}

long long get_lca(long long a, long long b)
{
    if (h[a] < h[b])
    {
        swap(a, b);
    }
    a = get_la(a, h[a] - h[b]);
    if (a == b)
    {
        return a;
    }

    for (long long i = LOG - 1; i > -1; i--)
    {
        if (binup[a][i] != binup[b][i])
        {
            a = binup[a][i];
            b = binup[b][i];
        }
    }
    return binup[a][0];
}

long long dist(long long a, long long b)
{
    long long c = get_lca(a, b);
    return h[a] + h[b] - h[c] * 2;
}

vector<pair<long long, long long>> tr[200000];
vector<long long> dp;

void calc_dp(long long v)
{
    dp[v] = 0;
    for (auto& i : tr[v])
    {
        calc_dp(i.first);
        dp[v] = max(dp[v], dp[i.first] + i.second);
    }
}

void solve()
{
    cin >> n;
    val.resize(n);
    pos.resize(n);
    h.resize(n);
    for (long long i = 0; i < n; i++)
    {
        cin >> val[i];
        val[i]--;
        pos[val[i]] = i;
    }
    for (long long i = 0; i < n - 1; i++)
    {
        long long a, b;
        cin >> a >> b;
        a--; b--;
        g[a].push_back(b);
        g[b].push_back(a);
    }
    for (long long i = 0; i < n; i++)
    {
        binup[i].resize(LOG);
    }
    build_binup(0, -1);

    dsu kek(n, val);
    for (long long ch = 0; ch < n; ch++)
    {
        long long v = pos[ch];
        for (auto& i : g[v])
        {
            if (val[i] > val[v])
            {
                continue;
            }

            long long to = pos[kek.mx[kek.rt(i)]];
            tr[v].push_back({ to, dist(v, to) });
            kek.unite(v, i);
        }
    }
    dp.resize(n);
    calc_dp(pos[n - 1]);
    cout << dp[pos[n - 1]] << "\n";
}

int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    srand(time(NULL));

    int tst = 1;
    //cin >> tst;
    while (tst--)
    {
        solve();
    }

    return 0;
}

/*
<3 <3 <3 <3 <3 <3 <3 <3 <3 <3 <3 <3 <3
⠀⠀⠀⠀⠀⠀⠀⠀⠀⣠⠤⠖⠚⢉⣩⣭⡭⠛⠓⠲⠦⣄⡀⠀⠀⠀⠀⠀⠀⠀
⠀⠀⠀⠀⠀⠀⢀⡴⠋⠁⠀⠀⠊⠀⠀⠀⠀⠀⠀⠀⠀⠀⠉⠳⢦⡀⠀⠀⠀⠀
⠀⠀⠀⠀⢀⡴⠃⢀⡴⢳⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠙⣆⠀⠀⠀
⠀⠀⠀⠀⡾⠁⣠⠋⠀⠈⢧⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠈⢧⠀⠀
⠀⠀⠀⣸⠁⢰⠃⠀⠀⠀⠈⢣⡀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠈⣇⠀
⠀⠀⠀⡇⠀⡾⡀⠀⠀⠀⠀⣀⣹⣆⡀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢹⠀
⠀⠀⢸⠃⢀⣇⡈⠀⠀⠀⠀⠀⠀⢀⡑⢄⡀⢀⡀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢸⡇
⠀⠀⢸⠀⢻⡟⡻⢶⡆⠀⠀⠀⠀⡼⠟⡳⢿⣦⡑⢄⠀⠀⠀⠀⠀⠀⠀⠀⢸⡇
⠀⠀⣸⠀⢸⠃⡇⢀⠇⠀⠀⠀⠀⠀⡼⠀⠀⠈⣿⡗⠂⠀⠀⠀⠀⠀⠀⠀⢸⠁
⠀⠀⡏⠀⣼⠀⢳⠊⠀⠀⠀⠀⠀⠀⠱⣀⣀⠔⣸⠁⠀⠀⠀⠀⠀⠀⠀⢠⡟⠀
⠀⠀⡇⢀⡇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠠⠀⡇⠀⠀⠀⠀⠀⠀⠀⠀⢸⠃⠀
⠀⢸⠃⠘⡇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢸⠁⠀⠀⢀⠀⠀⠀⠀⠀⣾⠀⠀
⠀⣸⠀⠀⠹⡄⠀⠀⠈⠁⠀⠀⠀⠀⠀⠀⠀⡞⠀⠀⠀⠸⠀⠀⠀⠀⠀⡇⠀⠀
⠀⡏⠀⠀⠀⠙⣆⠀⠀⠀⠀⠀⠀⠀⢀⣠⢶⡇⠀⠀⢰⡀⠀⠀⠀⠀⠀⡇⠀⠀
⢰⠇⡄⠀⠀⠀⡿⢣⣀⣀⣀⡤⠴⡞⠉⠀⢸⠀⠀⠀⣿⡇⠀⠀⠀⠀⠀⣧⠀⠀
⣸⠀⡇⠀⠀⠀⠀⠀⠀⠉⠀⠀⠀⢹⠀⠀⢸⠀⠀⢀⣿⠇⠀⠀⠀⠁⠀⢸⠀⠀
⣿⠀⡇⠀⠀⠀⠀⠀⢀⡤⠤⠶⠶⠾⠤⠄⢸⠀⡀⠸⣿⣀⠀⠀⠀⠀⠀⠈⣇⠀
⡇⠀⡇⠀⠀⡀⠀⡴⠋⠀⠀⠀⠀⠀⠀⠀⠸⡌⣵⡀⢳⡇⠀⠀⠀⠀⠀⠀⢹⡀
⡇⠀⠇⠀⠀⡇⡸⠁⠀⠀⠀⠀⠀⠀⠀⠀⠀⠙⠮⢧⣀⣻⢂⠀⠀⠀⠀⠀⠀⢧
⣇⠀⢠⠀⠀⢳⠇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠈⡎⣆⠀⠀⠀⠀⠀⠘
⢻⠀⠈⠰⠀⢸⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠰⠘⢮⣧⡀⠀⠀⠀⠀
⠸⡆⠀⠀⠇⣾⠀⠀⠀⠀⠀⠀⠀⠀⠀⢠⠆⠀⠀⠀⠀⠀⠀⠀⠙⠳⣄⡀⢢⡀
<3 <3 <3 <3 <3 <3 <3 <3 <3 <3 <3 <3 <3
*/

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• Subtask 2: 7 / 7
• Subtask 3: 7 / 7
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• Subtask 7: 26 / 26