Submission #955497

#	Time	Username	Problem	Language	Result	Execution time	Memory
955497		yoav_s	Newspapers (CEOI21_newspapers)	C++17	20 / 100	1096 ms	856 KiB

newspapers

#include <bits/stdc++.h>

using namespace std;

typedef short ll;
typedef vector<ll> v;
typedef vector<v> vv;
typedef vector<vv> vvv;
typedef pair<ll,ll> p;
typedef vector<p> vp;
typedef vector<vp> vvp;
typedef vector<vvp> vvvp;
typedef pair<ll, p> tri;
typedef vector<tri> vtri;
typedef vector<vtri> vvtri;
typedef vector<vvtri> vvvtri;
typedef vector<bool> vb;
typedef vector<vb> vvb;
typedef vector<vvb> vvvb;

#define f first
#define s second
#define pb push_back
#define eb emplace_back
#define all(v) (v).begin(),(v).end()

const ll INF = 1e18;
const ll mod = 1e9 + 7;

void eulerTour(ll i, v &visited, vv &graph, v &res, ll &uniqCount, ll nonLeafCount)
{
    res.pb(i);
    visited[i]++;
    uniqCount++;

    for (ll x : graph[i])
    {
        if (visited[x] == 0 && graph[x].size() > 1)
        {
            eulerTour(x,visited,graph,res,uniqCount, nonLeafCount);
            if (uniqCount < nonLeafCount)
            {
                res.pb(i);
                visited[i]++;
            }
        }
    }
}

ll nonLeafSubtreeCount(ll i, v &res, vv &graph)
{
    if (res[i] != -1 || graph[i].size() == 1) return 0;
    res[i] = 1;
    for (ll x : graph[i]) res[i] += nonLeafSubtreeCount(x, res, graph);
    return res[i];
}

bool simulate(v &order, vector<bitset<1000>> &graph)
{
    ll N = graph.size();
    bitset<1000> available;
    for (ll i=  0; i < N; i++) available[i] = 1;
    bool poss = true;
    for (ll x : order)
    {
        available[x] = 0;
        bitset<1000> newGeneration;
        for (ll i = 0; i < N; i++)
        {
            if (available[i]) newGeneration |= graph[i];
        }
        available = newGeneration;
    }
    return available.none();
}

int main()
{
    ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL);
    ll N, M;
    cin >> N >> M;
    vv graph(N);
    for (ll i=  0; i < M; i++)
    {
        ll a, b;
        cin >> a >> b;
        graph[a-1].pb(b-1);
        graph[b-1].pb(a-1);
    }
    if (M != N - 1)
    {
        cout << "NO\n";
        return 0;
    }
    //theory - find euler tour, check if visiting a vertex thrice (at least). if yes, then NO. otherwise check if works. if not, repeat twice
    if (N == 1)
    {
        cout << "YES\n1\n1\n";
        return 0;
    }
    if (N == 2)
    {
        cout << "YES\n2\n1 1\n";
        return 0;
    }
    ll mini = INF;
    v minTour;
    v order(N);
    for (ll i=  0; i < N; i++) order[i] = i;
    random_shuffle(all(order));
    vector<bitset<1000>> graphAlt(N);
    for (ll i = 0; i < N; i++) for (ll x : graph[i]) graphAlt[i][x] = 1;
    for (ll j=  0; j < N; j++)
    {
        ll i = order[j];
        if (graph[i].size() == 1) continue;
        ll valid = 0;
        for (ll x : graph[i]) if (graph[x].size() > 1) valid++;
        if (valid > 1) continue;
        v nonLeafSubtreeCounts(N, -1); nonLeafSubtreeCount(i, nonLeafSubtreeCounts, graph);
        for (ll i = 0; i < N; i++) sort(all(graph[i]),[&nonLeafSubtreeCounts](ll i, ll j){return nonLeafSubtreeCounts[i] < nonLeafSubtreeCounts[j];});
        ll cnt = 0;
        v visited(N, 0);
        v tour;
        ll nonLeafCount = 0;
        for (auto x : graph) if (x.size() != 1) nonLeafCount++;
        eulerTour(i, visited, graph, tour, cnt, nonLeafCount);
        v res;
        if (simulate(tour, graphAlt))
        {
            res = tour;
        }
        else
        {
            v newTour1;
            for (ll x : tour) newTour1.pb(x);
            for (ll x : tour) newTour1.pb(x);
            if (simulate(newTour1, graphAlt)) res = newTour1;
            else
            {
                v newTour2;
                for (ll x : tour) newTour2.pb(x);
                for (ll i = tour.size() - 1; i >= 0; i--) newTour2.pb(tour[i]);
                if (simulate(newTour2, graphAlt)) res = newTour2;
            }
        }
        if (res.size() > 0)
        {
            mini = res.size();
            minTour = res;
            break;
        }
    }
    if (mini == INF)
    {
        cout << "NO\n"; return 0;
    }
    cout << "YES\n";
    cout << mini << "\n";
    for (ll x : minTour) cout << x + 1 << " ";
    cout << "\n";
    return 0;
}

Compilation message (stderr)

newspapers.cpp:27:16: warning: overflow in conversion from 'double' to 'll' {aka 'short int'} changes value from '1.0e+18' to '32767' [-Woverflow]
   27 | const ll INF = 1e18;
      |                ^~~~
newspapers.cpp:28:20: warning: overflow in conversion from 'double' to 'll' {aka 'short int'} changes value from '1.000000007e+9' to '32767' [-Woverflow]
   28 | const ll mod = 1e9 + 7;
      |                ~~~~^~~
newspapers.cpp: In function 'bool simulate(v&, std::vector<std::bitset<1000> >&)':
newspapers.cpp:63:10: warning: unused variable 'poss' [-Wunused-variable]
   63 |     bool poss = true;
      |          ^~~~

• Subtask 1: 12 / 12
• Subtask 2: 8 / 8
• Subtask 3: 0 / 80