oj.uz

Submission #656257

# Submission time Handle Problem Language Result Execution time Memory
656257 2022-11-06T16:11:34 Z ilia_rr Network (BOI15_net) C++17
0 / 100
 31 ms 55124 KB 
// بِسْمِ اللَّهِ الرَّحْمَنِ الرَّحِيمِ
// Written by Ilia Rahbar

// #pragma GCC optimize ("O3,no-stack-protector,unroll-loops,fast-math")
// #pragma GCC target ("abm,bmi,bmi2,tbm,avx2")

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

#define int int64_t
#define ai(x) array <int, x>
#define F first 
#define S second

const int MOD = 1e9 + 7, N = 1e6 + 100;

int q, c, n, u, v, d[N], stc, l, r;

vector <int> g[N], st[N], ans[2];

int ffv(int inx)
{
    memset(d, 0, sizeof d);

    queue <int> q;

    d[inx] = 1;
    q.push(inx);

    while (q.size())
    {
        inx = q.front();
        q.pop();

        for (auto i : g[inx])
        {
            if (!d[i])
            {
                d[i] = d[inx] + 1;

                q.push(i);
            }
        }
    }
    
    return inx;
}

void dfs(int inx)
{
    if (g[inx].size() == 1)
        st[stc].push_back(inx);

    for (auto i : g[inx])
    {
        if (!d[i])
        {
            d[i] = 1;

            dfs(i);
        }
    }
}

int32_t main()
{
    ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
    
    cin >> n;

    for (int i = 1; i < n; i++)
        cin >> u >> v, g[u].push_back(v), g[v].push_back(u);

    q = ffv(1);

    q = ffv(q);

    for (int i = 1; i <= n; i++)
    {
        if (d[i] == (d[q] + 1) / 2)
        {
            c = i;
            
            break;
        }
    }

    memset(d, 0, sizeof d);

    d[c] = 1;

    for (auto i : g[c])
    {
        dfs(i);

        stc++;
    }

    sort(st, st+stc, [](vector <int> &x, vector <int> &y){return (x.size() < y.size());});
    
    l = 0;
    r = stc-1;

    while (st[r].size())
    {
        for (int i = r-1; st[r].size() && i >= l; i--)
        {
            ans[0].push_back(st[r].back());
            ans[1].push_back(st[i].back());

            st[r].pop_back();
            st[i].pop_back();
        }
        
        while (l < r && st[r].empty())
            r--;

        while (l < r && st[l].empty())
            l++;

        if (l == r)
        {
            while (st[r].size())
            {
                ans[0].push_back(st[r].back());
                
                st[r].pop_back();
                
                if (st[r].size())
                {
                    ans[1].push_back(st[r].back());
                    st[r].pop_back();
                }

                else
                    ans[1].push_back(c);
            }
        }
    }

    cout << ans[0].size() << "\n";

    for (int i = 0; i < int(ans[0].size()); i++)
        cout << ans[0][i] << " " << ans[1][i] << "\n";
}

Subtask #1
0 / 18.0

# Verdict Execution time Memory Grader output
1 Correct 27 ms 54988 KB Output is correct
2 Correct 28 ms 55036 KB Output is correct
3 Correct 28 ms 55092 KB Output is correct
4 Correct 28 ms 55100 KB Output is correct
5 Correct 27 ms 55100 KB Output is correct
6 Correct 30 ms 55060 KB Output is correct
7 Correct 29 ms 54988 KB Output is correct
8 Correct 31 ms 55008 KB Output is correct
9 Correct 28 ms 55124 KB Output is correct
10 Correct 30 ms 55076 KB Output is correct
11 Correct 28 ms 55016 KB Output is correct
12 Correct 28 ms 55048 KB Output is correct
13 Correct 28 ms 55036 KB Output is correct
14 Correct 27 ms 55020 KB Output is correct
15 Correct 29 ms 54996 KB Output is correct
16 Correct 28 ms 54996 KB Output is correct
17 Incorrect 31 ms 54996 KB Invalid number of links.
18 Halted 0 ms 0 KB -

Subtask #2
0 / 45.0

# Verdict Execution time Memory Grader output
1 Correct 27 ms 54988 KB Output is correct
2 Correct 28 ms 55036 KB Output is correct
3 Correct 28 ms 55092 KB Output is correct
4 Correct 28 ms 55100 KB Output is correct
5 Correct 27 ms 55100 KB Output is correct
6 Correct 30 ms 55060 KB Output is correct
7 Correct 29 ms 54988 KB Output is correct
8 Correct 31 ms 55008 KB Output is correct
9 Correct 28 ms 55124 KB Output is correct
10 Correct 30 ms 55076 KB Output is correct
11 Correct 28 ms 55016 KB Output is correct
12 Correct 28 ms 55048 KB Output is correct
13 Correct 28 ms 55036 KB Output is correct
14 Correct 27 ms 55020 KB Output is correct
15 Correct 29 ms 54996 KB Output is correct
16 Correct 28 ms 54996 KB Output is correct
17 Incorrect 31 ms 54996 KB Invalid number of links.
18 Halted 0 ms 0 KB -

Subtask #3
0 / 37.0

# Verdict Execution time Memory Grader output
1 Correct 27 ms 54988 KB Output is correct
2 Correct 28 ms 55036 KB Output is correct
3 Correct 28 ms 55092 KB Output is correct
4 Correct 28 ms 55100 KB Output is correct
5 Correct 27 ms 55100 KB Output is correct
6 Correct 30 ms 55060 KB Output is correct
7 Correct 29 ms 54988 KB Output is correct
8 Correct 31 ms 55008 KB Output is correct
9 Correct 28 ms 55124 KB Output is correct
10 Correct 30 ms 55076 KB Output is correct
11 Correct 28 ms 55016 KB Output is correct
12 Correct 28 ms 55048 KB Output is correct
13 Correct 28 ms 55036 KB Output is correct
14 Correct 27 ms 55020 KB Output is correct
15 Correct 29 ms 54996 KB Output is correct
16 Correct 28 ms 54996 KB Output is correct
17 Incorrect 31 ms 54996 KB Invalid number of links.
18 Halted 0 ms 0 KB -