Submission #79535

#	Time	Username	Problem	Language	Result	Execution time	Memory
79535		Vinhspm	Network (BOI15_net)	C++14	0 / 100	2 ms	588 KiB

net

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

#define fi first
#define se second
#define pb push_back

typedef pair<int, int> ii;

const int N = 5e5 + 10;
const int oo = 1e9;

int n;
int deg[N];

signed main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(0); cout.tie(0);
    cin >> n;
    for(int i = 1; i < n; ++i) {
        int u, v; cin >> u >> v;
        deg[u] ++; deg[v] ++;
    }
    vector<ii> ans;
    int las = -1;
    for(int i = 1; i <= n; ++i) if(deg[i] == 1) {
        if(las == -1) las = i;
        else ans.pb({i, las}), las = -1;
    }
    if(las != -1) for(int i = 1; i <= n; ++i) if(deg[i] == 1) {
        ans.pb(ii(las, i)); break;
    }
    cout << ans.size() << '\n';
    for(ii v: ans) cout << v.fi << ' ' << v.se << '\n';
}

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