Submission #1206712

#	Time	Username	Problem	Language	Result	Execution time	Memory
1206712		dksnfjkfnwkfw	Network (BOI15_net)	C++20	0 / 100	12 ms	23880 KiB

net

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

#define sonic ios_base::sync_with_stdio(false);cin.tie(0); cout.tie(0)
#define IO(main) if(fopen(main".inp","r")){freopen(main".inp","r",stdin);freopen(main".out","w",stdout);}
#define pb push_back
#define fi first
#define se second
#define mp make_pair
#define ins insert
#define pb push_back
#define el cout << endl
#define SZ(x) ((int)(x).size())
#define ALL(x) (x).begin(), (x).end()
#define MASK(i) ((1LL)<<(i))
#define BIT(x,i) (((x)>>(i))&(1LL))
#define FOR(i, a, b) for(int (i)=(a);(i)<=(b); i++)
#define FORD(i, a, b) for(int (i)=(a);(i)>=(b); i--)


using ll = long long;
using ull = unsigned long long;
using ld = long double;

using pii = pair<int, int>;
using pll = pair<ll, ll>;
using vi = vector<int>;
using vii = vector<pii>;

const int N = 1e6 + 9;
const int mod = 1e9 + 7;
const ll INF = 1e18 + 7;
const int base = 31;
const int LOG = 20;
const ll MOD = 1e9 + 7;

int mul(int x, int y) {return 1LL * x * y % mod;}
int calPw(int x, int y)
{
    int ans = 1;
    while(y)
    {
        if (y&1) ans = 1LL * ans * x % mod;
        x = 1LL * x * x % mod;
        y >>= 1;
    }
    return ans;
}
int d4x[4] = {1, 0, -1, 0};
int d4y[4] = {0, 1, 0, -1};
int dx[8] = {0, 1, 1, 1, 0, -1, -1, -1};
int dy[8] = {1, 1, 0, -1, -1, -1, 0, 1};
///Author: Le Chi Thien Luong The Vinh high school 2008
///code
template<class X, class Y>
bool minimize(X &x , Y y){
    if(x > y){
        x = y;
        return true;
    }
    return false;
}
template<class X, class Y>
bool maximize(X &x , Y y){
    if(x < y){
        x = y;
        return true;
    }
    return false;
}
template<class X, class Y>
bool add(X &x , Y y){
    if((x + y ) >= mod){
        ll tmp  = x + y;
        x = tmp - mod;
        return true;
    }
    return false;
}
void Solve(){

}
int n;
int used[N];
vector<int>adj[N];
int bac[N];
void Read(){
    cin >> n ;
    FOR(i, 2, n){
        int u, v;
        cin >> u >> v;
        adj[u].push_back(v);
        adj[v].push_back(u);
        bac[u]++;
        bac[v]++;
    }
    vector<int>v;
    FOR(i, 1, n)if(bac[i] == 1)v.push_back(i);
    int ans = v.size();
    ans = (ans + 1)/2;
  ///  for(int c : v)cout <<c << " ";el;
        vector<pii>res;
        FOR(x, 0, v.size() - 1){
            FOR(y, 0, v.size() - 1){
                int i = v[x];
                int j = v[y];
                if(i!=j)
                if(used[i] == 0 && used[j] == 0){
                  ///  cout << i << " " << j << endl;
                    res.push_back({i, j});
                    used[i] = 1;
                    used[j] = 1;
                }
            }
        }
        int id =-1;
        FOR(i, 0, v.size() - 1){
            if(used[v[i]] == 0){
                id = v[i];
                break;
            }
        }
       /// cout << id << endl;
        FOR(i, 1, n)if(id!=i && id != -1 && used[i] == 0){
            res.push_back({i, id});
            break;
        }
        cout << ans << endl;
        for(pii x : res)cout << x.fi << " " << x.se << endl;
}



int main()
{
    sonic;

    int TEST = 1;
   // cin >> TEST;
    while(TEST--)
    {

        Read();
        Solve();
    }
}

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