Submission #1091424

#	Time	Username	Problem	Language	Result	Execution time	Memory
1091424		andrei_iorgulescu	Joker (BOI20_joker)	C++14	100 / 100	466 ms	20636 KiB

Joker

#include <bits/stdc++.h>

using namespace std;

int n, m, q;
int u[200005], v[200005];
int rmin[200005];

pair<int, int> t[200005];
int sz[200005];
bool bip[200005];
int cnt_bad;
int curi;

struct ura
{
    int tip;///0 pentru p1.first != p2.first, 1 pentru celalalt
    int idx = 0, x = 0, y = 0;
    bool bipant = false;
};

vector<ura> op;

pair<int, int> par(int x)
{
    int ugabuga = 0;
    int s1 = 0;
    while (t[x].first != x)
    {
        s1 += t[x].second;
        x = t[x].first;
    }
    return make_pair(x, s1);
}

void join(int idx, int x, int y)
{
    //cout << idx << ' ' << x << ' ' << y << endl;
    pair<int,int> p1 = par(x);
    pair<int,int> p2 = par(y);
    //cout << x << ' ' << y << endl;
    if (p1.first != p2.first)
    {
        if (sz[p1.first] < sz[p2.first])
            swap(p1, p2);
        //cout << "c1" << endl;
        t[p2.first] = {p1.first, (1 + p1.second + p2.second) % 2};
        sz[p1.first] += sz[p2.first];
        ura aux;
        aux.tip = 0;
        aux.idx = idx, aux.x = p1.first, aux.y = p2.first;
        aux.bipant = bip[p1.first];
        if (bip[p1.first] == false and bip[p2.first] == false)
            cnt_bad--;
        if (bip[p2.first] == false)
            bip[p1.first] = false;
        op.push_back(aux);
    }
    else
    {
        ura aux;
        aux.tip = 1;
        aux.idx = idx;
        aux.x = p1.first;
        aux.y = p2.first;
        aux.bipant = bip[p1.first];
        if (p1.second % 2 == p2.second % 2 and bip[p1.first] == true)
        {
            //cout << "cmon" << p1.first << endl;
            bip[p1.first] = false;
            cnt_bad++;
        }
        op.push_back(aux);
    }
}

void und(ura uf)
{
    //cout << "und" << uf.idx << endl;
    if (uf.tip == 0)
    {
        if (bip[uf.y] == false and uf.bipant == false)
            cnt_bad++;
        bip[uf.x] = uf.bipant;
        sz[uf.x] -= sz[uf.y];
        t[uf.y] = {uf.y, 0};
    }
    else
    {
        if (bip[uf.x] != uf.bipant)
            cnt_bad--;
        bip[uf.x] = uf.bipant;
    }
}

bool cmp(ura A, ura B)
{
    if ((A.idx < curi and B.idx >= curi) or (A.idx >= curi and B.idx < curi))
        return A.idx < B.idx;
    else if (A.idx < curi)
        return A.idx < B.idx;
    else
        return A.idx > B.idx;
}

void undo(int idx)
{
    //cout << "u" << idx << endl;
    vector<ura> cur;
    int cate = 0;
    while (true)
    {
        cur.push_back(op.back());
        op.pop_back();
        cate++;
        if (cur.back().idx == idx)
            break;
    }
    while (cate != 0 and !op.empty())
    {
        cur.push_back(op.back());
        op.pop_back();
        cate--;
    }
    for (auto it : cur)
        und(it);
    sort(cur.begin(), cur.end(), cmp);
    for (auto it : cur)
        if (it.idx != idx)
            join(it.idx, u[it.idx], v[it.idx]);
}

int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);
    cin >> n >> m >> q;
    for (int i = 1; i <= m; i++)
        cin >> u[i] >> v[i];
    for (int i = 1; i <= n; i++)
    {
        t[i] = {i, 0};
        sz[i] = 1;
        bip[i] = true;
    }
    for (int i = 1; i <= m; i++)
        join(i, u[i], v[i]);
    //cout << cnt_bad << endl;
    if (cnt_bad == 0)
    {
        for (int i = 1; i <= q; i++)
        {
            int x, y;
            cin >> x >> y;
            cout << "NO\n";
        }
        return 0;
    }
    int r = 0;
    for (int i = 1; i <= m; i++)
    {
        curi = i;
        while (r < m and cnt_bad > 0)
        {
            r++;
            undo(r);
        }
        if (cnt_bad != 0)
        {
            rmin[i] = m + 1;
            continue;
        }
        rmin[i] = r;
        join(i, u[i], v[i]);
    }
    //for (int i = 1; i <= m; i++)
      //  cout << rmin[i] << ' ';
    //cout << endl;
    for (int i = 1; i <= q; i++)
    {
        int x, y;
        cin >> x >> y;
        if (y < rmin[x])
            cout << "YES\n";
        else
            cout << "NO\n";
    }
    return 0;
}

/**
deci teoretic daca bag elementele de la 1 la N, apoi fac two pointers-ul, o sa cam am queue-like undoing pe DSU, pe care tin si ceva de bipartit
**/

Compilation message (stderr)

Joker.cpp: In function 'std::pair<int, int> par(int)':
Joker.cpp:26:9: warning: unused variable 'ugabuga' [-Wunused-variable]
   26 |     int ugabuga = 0;
      |         ^~~~~~~

• Subtask 1: 6 / 6
• Subtask 2: 8 / 8
• Subtask 3: 25 / 25
• Subtask 4: 10 / 10
• Subtask 5: 22 / 22
• Subtask 6: 29 / 29