Submission #926395

#	Time	Username	Problem	Language	Result	Execution time	Memory
926395		Regulus	Network (BOI15_net)	C++17	0 / 100	3 ms	12124 KiB

net

#include <bits/stdc++.h>
#define IO ios::sync_with_stdio(false);cin.tie(0);
#define debug(x) cerr << #x << " = " << (x) << ' '
#define bug(x) cerr << (x) << ' '
#define endl cerr << '\n'
#define all(v) (v).begin(), (v).end()
#define SZ(v) (ll)(v).size()
#define lowbit(x) (x)&-(x)
#define pb emplace_back
#define F first
#define S second
using namespace std;
using ll = long long;
using pll = pair<ll, ll>;

const int N = 5e5+5;
vector<int> g[N], vec;

inline void dfs(int x, int pre)
{
    if (SZ(g[x]) == 1) vec.pb(x);
    for (int v : g[x]) if (v != pre) dfs(v, x);
}

int main(void)
{ IO
    int n, i;
    
    cin >> n;
    for (i=0; i < n-1; ++i)
    {
        int x, y; cin >> x >> y;
        g[x].pb(y), g[y].pb(x);
    }

    dfs(1, 0);
    cout << ((SZ(vec)+1)>>1) << '\n';
    for (i=1; i < SZ(vec); i+=2) cout << vec[i-1] << ' ' << vec[i] << '\n';
    if (SZ(vec) & 1) cout << vec[0] << ' ' << vec.back() << '\n';


    return 0;
}

• Subtask 1: 0 / 18
• Subtask 2: 0 / 45
• Subtask 3: 0 / 37