Submission #1312977

#	Time	Username	Problem	Language	Result	Execution time	Memory
1312977		4QT0R	Sumtree (INOI20_sumtree)	C++20	10 / 100	283 ms	31708 KiB

Main

#include <bits/stdc++.h>
using namespace std;
#define ll long long

const ll mod = 1e9 + 7;

vector<ll> graph[200003];
ll fat[200003];
ll label_sum[200003];
ll label[200003];
ll siz[200003];
ll iter, seg_iter;

void prep(ll v, ll p)
{
    fat[v] = p;
    siz[v] = 1;
    for (auto u : graph[v])
    {
        if (u == p)
            continue;
        prep(u, v);
        siz[v] += siz[u];
    }
}

ll fact[500003];
ll fact_inv[500003];

ll fast_pow(ll a, ll b)
{
    if (b == 1)
        return a;
    ll cur = fast_pow(a, b / 2);
    cur = (cur * cur) % mod;
    if (b & 1)
        cur = (cur * a) % mod;
    return cur;
}

void init(ll &n, ll &r, ll &q)
{
    cin >> n >> r;
    for (ll i = 1, a, b; i < n; i++)
    {
        cin >> a >> b;
        graph[a].push_back(b);
        graph[b].push_back(a);
    }
    cin >> q;

    fill(label + 1, label + n + 1, -1);

    fact[0] = 1;
    for (ll i = 1; i <= 500002; i++)
        fact[i] = (i * fact[i - 1]) % mod;
    fact_inv[500002] = fast_pow(fact[500002], mod - 2);
    for (ll i = 500001; i >= 0; i--)
        fact_inv[i] = ((i + 1) * fact_inv[i + 1]) % mod;
}

ll res(ll siz, ll tag)
{
    ll wyn = fact[siz + tag - 1];
    wyn = (wyn * fact_inv[tag]) % mod;
    wyn = (wyn * fact_inv[siz - 1]) % mod;
    return wyn;
}

ll Find(ll v)
{
    if (label[v] >= 0)
        return v;
    return Find(fat[v]);
}

void add(ll v, ll x, ll y)
{
    while (v)
    {
        siz[v] += x;
        label_sum[v] += y;
        v = fat[v];
    }
}

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

    ll n, r, q;
    init(n, r, q);

    prep(1, 0);
    label_sum[1] = r;
    label[1] = r;

    ll ans = res(n, label_sum[1]), neg_vert = 0;
    cout << ans << '\n';
    for (ll i = 1, t, v, tag; i <= q; i++)
    {
        cin >> t >> v;
        if (t == 1)
            cin >> tag;

        ll up = Find(fat[v]);

        if (label_sum[up] < 0)
            neg_vert--;
        else
            ans = (ans * fast_pow(res(siz[up], label_sum[up]), mod - 2)) % mod;

        if (t == 1)
        {
            label[v] = tag;
            label_sum[v] += tag;

            add(fat[v], -siz[v], -label[v]);
            add(fat[up], siz[v], label[v]);

            label_sum[up] -= label_sum[v];
            if (label_sum[v] < 0)
                neg_vert++;
            else
                ans = (ans * res(siz[v], label_sum[v])) % mod;
        }
        else
        {
            if (label_sum[v] < 0)
                neg_vert--;
            else
                ans = (ans * fast_pow(res(siz[v], label_sum[v]), mod - 2)) % mod;
            label_sum[up] += label_sum[v];

            add(fat[up], -siz[v], -label[v]);
            add(fat[v], siz[v], label[v]);

            label_sum[v] -= label[v];
            label[v] = -1;
        }

        if (label_sum[up] < 0)
            neg_vert++;
        else
            ans = (ans * res(siz[up], label_sum[up])) % mod;

        if (neg_vert)
            cout << "0\n";
        else
            cout << ans << '\n';
    }
}

• Subtask 1: 10 / 10
• Subtask 2: 0 / 20
• Subtask 3: 0 / 20
• Subtask 4: 0 / 20
• Subtask 5: 0 / 30