# | Time | Username | Problem | Language | Result | Execution time | Memory |
---|---|---|---|---|---|---|---|
443499 | BeanZ | Network (BOI15_net) | C++14 | 538 ms | 64448 KiB |
This submission is migrated from previous version of oj.uz, which used different machine for grading. This submission may have different result if resubmitted.
// I_Love_LPL 1y0m2d
#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define endl '\n'
const int N = 1e6 + 5;
long long mod = 1000007;
const int lim = 4e5 + 5;
const int lg = 20;
const int base = 311;
const long double eps = 1e-6;
vector<ll> node[N];
vector<ll> one;
void dfs(ll u, ll p){
for (auto j : node[u]){
if (j == p) continue;
dfs(j, u);
}
if (node[u].size() == 1) one.push_back(u);
}
int main(){
ios_base::sync_with_stdio(false);
cin.tie(0);
if (fopen("tests.inp", "r")){
freopen("test.inp", "r", stdin);
freopen("test.out", "w", stdout);
}
ll n;
cin >> n;
for (int i = 1; i < n; i++){
ll u, v;
cin >> u >> v;
node[u].push_back(v);
node[v].push_back(u);
}
for (int i = 1; i <= n; i++){
if (node[i].size() != 1){
dfs(i, i);
break;
}
}
cout << (one.size() + 1) / 2 << endl;
for (int i = 0; i < (one.size() + 1) / 2; i++){
cout << one[i] << " " << one[i + one.size() / 2] << endl;
}
}
/*
Ans:
Out:
*/
Compilation message (stderr)
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