This submission is migrated from previous version of oj.uz, which used different machine for grading. This submission may have different result if resubmitted.
#include<bits/stdc++.h> //:3
using namespace std;
typedef long long ll;
#define all(a) (a).begin(), (a).end()
#define ff first
#define ss second
#define pb push_back
#define mp make_pair
#define pi pair<int, int>
#define sz(x) (int)((x).size())
//#define int long long
const int dx[] = {0, 1, 0, -1};
const int dy[] = {1, 0, -1, 0};
const ll inf = 2e9;
const ll mod = 1e9 + 7;
const int N = 2e6 + 11;
const ll INF64 = 3e18 + 1;
const double eps = 1e-14;
const double PI = acos(-1);
//ifstream in(".in");
//ofstream out(".out");
int n, m;
vector<int>v[N];
void solve(){
cin >> n;
for(int i = 1, x, y; i < n; i++){
cin >> x >> y;
v[x].push_back(y);
v[y].push_back(x);
}
int root = 0;
vector<int>leaves;
for(int i = 1; i <= n; i++){
if(sz(v[i]) == 1){
leaves.push_back(i);
}
if(sz(v[i]) > 1)root = i;
}
int ans = sz(leaves)/2 + sz(leaves) % 2;
cout << ans << '\n';
cout << "L" <<'\n';
for(auto it : leaves)cout << it << ' '; cout << '\n';
//cout << "R = " << root << '\n';
for(int i = 0; i < ans; i ++){
cout << leaves[i] << ' ' << leaves[i + sz(leaves)/2] << '\n';
}
}
int32_t main(){
ios_base :: sync_with_stdio(0); cin.tie(0); cout.tie(0);
int T = 1;
//cin >> T;
while(T--){
solve();
}
}
Compilation message (stderr)
net.cpp: In function 'void solve()':
net.cpp:53:5: warning: this 'for' clause does not guard... [-Wmisleading-indentation]
53 | for(auto it : leaves)cout << it << ' '; cout << '\n';
| ^~~
net.cpp:53:45: note: ...this statement, but the latter is misleadingly indented as if it were guarded by the 'for'
53 | for(auto it : leaves)cout << it << ' '; cout << '\n';
| ^~~~
net.cpp:39:9: warning: variable 'root' set but not used [-Wunused-but-set-variable]
39 | int root = 0;
| ^~~~
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