Submission #79580

#	Time	Username	Problem	Language	Result	Execution time	Memory
79580		Vinhspm	Network (BOI15_net)	C++14	100 / 100	699 ms	45592 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, cnt;
int leaf[N];
bool visit[N];
vector<int> lef, rig, vi[N];

void dfs(int pre, int u)    {
    for(int v: vi[u]) if(v != pre)
        dfs(u, v);
    if(vi[u].size() == 1) leaf[++cnt] = u;
}

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;
        vi[u].pb(v); vi[v].pb(u);
    }
    dfs(1, 1);
    cout << (cnt + 1) / 2 << '\n' ;
    for(int i = 1; i <= cnt / 2; ++i) cout << leaf[i] << ' ' << leaf[i + cnt / 2] << '\n' ;
    if(cnt % 2 == 1) cout << leaf[cnt] << ' ' << leaf[cnt - 1] << '\n';
}

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