Submission #993842

#	Time	Username	Problem	Language	Result	Execution time	Memory
993842		danikoynov	Wells (CEOI21_wells)	C++14	0 / 100	137 ms	17244 KiB

wells

#include<bits/stdc++.h>
#define endl '\n'

using namespace std;
typedef long long ll;

void speed()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);
}

const int maxn = 1e4 + 10;

int n, k;
vector < int > adj[maxn];

int dist[maxn];
int from[maxn];
void bfs(int v)
{
    for (int i = 1; i <= n; i ++)
        dist[i] = -1;

    queue < int > q;
    q.push(v);
    dist[v] = 0;
    while(!q.empty())
    {
        v = q.front();
        q.pop();
        for (int u : adj[v])
        {
            if (dist[u] == -1)
            {
                from[u] = v;
                dist[u] = dist[v] + 1;
                q.push(u);
            }
        }
    }
}

int forb[maxn], path[maxn][maxn];
void bfs_forb(int v)
{
        for (int i = 1; i <= n; i ++)
        dist[i] = -1;

    queue < int > q;
    q.push(v);
    dist[v] = 0;
    while(!q.empty())
    {
        v = q.front();
        q.pop();
        for (int u : adj[v])
        {
            if (forb[u] == 0 && dist[u] == -1)
            {
                from[u] = v;
                dist[u] = dist[v] + 1;
                q.push(u);
            }
        }
    }
}

int bruh[maxn][maxn];
void solve()
{
    cin >> n >> k;
    for (int i = 1; i < n; i ++)
    {
        int v, u;
        cin >> v >> u;
        adj[v].push_back(u);
        adj[u].push_back(v);
    }
    for (int i = 1; i <= n; i ++)
    {
        bfs(i);
        for (int j = 1; j <= n; j ++)
            path[i][j] = dist[j];
    }

   for (int v = 1; v <= n; v ++)
    {
        for (int u = v; u <= n; u ++)
        {
           // cout << v << " : " << u << endl;
            if (path[v][u] >= k - 1)
            {
               /// cout << v << " :" << u << endl;
                bfs(v);
                ///cout << "shiit" << endl;
                //for (int i = 1; i <= n; i ++)
                {
                  //  cout << "vertex " << i << " " << from[i] << endl;
                }
                int cur = u;
                vector < int > st;
                while(cur != v)
                {
                    ///cout << cur << endl;
                    st.push_back(cur);
                    cur = from[cur];
                }
                st.push_back(cur);
                for (int d : st)
                    for (int p : st)
                    bruh[d][p] = bruh[p][d] = 1;
            }
        }
    }

    /**for (int i = 1; i <= n; i ++, cout << endl)
        for (int j = 1; j <= n; j ++)
        cout << bruh[i][j] << " ";*/

    bfs(1);
    int mx = 1;
    for (int i = 1; i <= n; i ++)
        if (dist[mx] < dist[i])
        mx = i;

    bfs(mx);
    int len = 0;
    for (int i = 1; i <= n; i ++)
        len = max(len, dist[i]);


    if (len < k - 1)
    {
        cout << "YES" << endl;
        cout << 0 << endl;
        return;
    }
    for (int s = 1; s <= n; s ++)
    {
        bfs(s);
        vector < int > st;
        for (int i = 1; i <= n; i ++)
            forb[i] = 0;
        for (int i = 1; i <= n; i ++)
        {
            if (dist[i] % k == 0)
            {
                forb[i] = 1;
                st.push_back(i);
            }
        }


        bool fine = true;
        for (int i = 0; i < st.size(); i ++)
            for (int j = i + 1; j < st.size(); j ++)
        {
            if (path[st[i]][st[j]] < k && bruh[st[i]][st[j]] == 1)
            {
                fine = false;
            }
        }

        if (!fine)
            continue;

        for (int i = 1; i <= n; i ++)
        {
            if (forb[i])
                continue;

            bfs_forb(i);
            ///cout << "start " << i << endl;
            for (int j = 1; j <= n; j ++)
                if (dist[j] + 1 >= k)
            {
                fine = false;
            }
        }

        if (fine)
        {
            cout << "YES" << endl;
            cout << 0 << endl;
            return;
        }
    }

    cout << "NO" << endl;
    cout << 0 << endl;
}

int main()
{
    ///speed();
    solve();
    return 0;
}

Compilation message (stderr)

wells.cpp: In function 'void solve()':
wells.cpp:157:27: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  157 |         for (int i = 0; i < st.size(); i ++)
      |                         ~~^~~~~~~~~~~
wells.cpp:158:35: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  158 |             for (int j = i + 1; j < st.size(); j ++)
      |                                 ~~^~~~~~~~~~~

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