Submission #1012617

#	Time	Username	Problem	Language	Result	Execution time	Memory
1012617		DaoMinh	Bridges (APIO19_bridges)	C++17	100 / 100	1427 ms	77124 KiB

bridges

#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using pii = pair<int, int>;
const int maxN = 1e5 + 1;
const int MOD = 1e9 + 7;
const int B = 1000;

int n, m, q;
int u[maxN], v[maxN], w[maxN];
int o[maxN], x[maxN], y[maxN];
int mark[maxN], ans[maxN];
vector<int> add[maxN];

struct TDSU
{
    vector<pii> S;
    vector<int> lab;
    void Init(int n)
    {
        lab.clear();
        lab.resize(n + 1, -1);
    }
    int Find(int u)
    {
        return lab[u] < 0 ? u : Find(lab[u]);
    }
    void Unite(int u, int v)
    {
        int f = Find(u), s = Find(v);
        if (f == s) return;
        if (lab[f] > lab[s]) swap(f, s);
        S.push_back({s, lab[s]});
        lab[f] += lab[s];
        lab[s] = f;
    }
    void rollback(int sz)
    {
        while (S.size() > sz)
        {
            int s = S.back().first;
            int f = lab[s];
            int sz = S.back().second;
            S.pop_back();
            lab[f] -= sz;
            lab[s] = sz;
        }
    }
} dsu;

void ReadInput()
{
    cin >> n >> m;
    for (int i = 1; i <= m; i++)
        cin >> u[i] >> v[i] >> w[i];
    cin >> q;
    for (int i = 1; i <= q; i++)
        cin >> o[i] >> x[i] >> y[i];
}

void Solve()
{
    for (int l = 1; l <= q; l += B)
    {
        int r = min(l + B - 1, q);
        fill(mark + 1, mark + m + 1, 0); //O(m)
        dsu.Init(n);
        vector<int> unchange, upd, calc;
        for (int i = l; i <= r; i++) //O(B)
        {
            if (o[i] == 1)
            {
                mark[x[i]] = 1;
                upd.push_back(i);
            }
            else
                calc.push_back(i);
        }
        for (int i = 1; i <= m; i++) //O(m)
            if (!mark[i])
                unchange.push_back(i);
        for (int i = l; i <= r; i++) // O(B ^ 2)
        {
            if (o[i] == 1)
                w[x[i]] = y[i];
            else
            {
                add[i - l].clear(); //avoid MLE
                for (int j : upd)
                    if (w[x[j]] >= y[i])
                        add[i - l].push_back(x[j]);
            }
        }
        sort(calc.begin(), calc.end(), [&](int i, int j)
        {
            return y[i] > y[j];
        }); //O(BlogB)
        sort(unchange.begin(), unchange.end(), [&](int i, int j)
        {
            return w[i] > w[j];
        }); //O(mlogm)
        int j = 0;
        for (int i : calc) //(mlogn + B^2logn)
        {
            while (j < unchange.size() && w[unchange[j]] >= y[i])
            {
                dsu.Unite(u[unchange[j]], v[unchange[j]]);
                j++;
            }

            int PrevSz = dsu.S.size();
            for (int k : add[i - l])
                dsu.Unite(u[k], v[k]);
            ans[i] = -dsu.lab[dsu.Find(x[i])];
            dsu.rollback(PrevSz); // O(B)
        }
    }
    //=> O((M + Q).logN.B) (smaller than this quite much because the actual size is Q / B);
    for (int i = 1; i <= q; i++)
        if (o[i] == 2) cout << ans[i] << '\n';
}

#define task ""
int main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    //freopen(task".INP", "r", stdin);
    //freopen(task".OUT", "w", stdout);
    int T = 1;
    //cin >> T;
    while (T--)
    {
        ReadInput();
        Solve();
    }
}

Compilation message (stderr)

bridges.cpp: In member function 'void TDSU::rollback(int)':
bridges.cpp:39:25: warning: comparison of integer expressions of different signedness: 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} and 'int' [-Wsign-compare]
   39 |         while (S.size() > sz)
      |                ~~~~~~~~~^~~~
bridges.cpp: In function 'void Solve()':
bridges.cpp:105:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  105 |             while (j < unchange.size() && w[unchange[j]] >= y[i])
      |                    ~~^~~~~~~~~~~~~~~~~

• Subtask 1: 13 / 13
• Subtask 2: 16 / 16
• Subtask 3: 17 / 17
• Subtask 4: 14 / 14
• Subtask 5: 13 / 13
• Subtask 6: 27 / 27