Submission #554248

#	Time	Username	Problem	Language	Result	Execution time	Memory
554248		farhan132	Network (BOI15_net)	C++17	100 / 100	411 ms	48632 KiB

net

/***Farhan132***/
//#pragma GCC optimize("Ofast")
//#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,avx2,fma")
//#pragma GCC optimization ("unroll-loops")
//#pragma GCC optimize("Ofast,fast-math")
 
#include <bits/stdc++.h>
 
 
 
using namespace std;
 
typedef long long ll;
typedef unsigned long long ull;
typedef double dd;
typedef vector<ll> vll;
typedef pair<ll , ll> ii;
typedef vector< ii > vii;
typedef pair < pair < ll , ll > , pair < ll , ll > > cm; 
typedef tuple < ll,  ll, ll > tp;
 
#define ff first
#define ss second
#define pb push_back
#define in insert
#define f0(b) for(int i=0;i<(b);i++)
#define f00(b) for(int j=0;j<(b);j++)
#define f1(b) for(int i=1;i<=(b);i++)
#define f11(b) for(int j=1;j<=(b);j++)
#define f2(a,b) for(int i=(a);i<=(b);i++)
#define f22(a,b) for(int j=(a);j<=(b);j++)
#define sf(a) scanf("%lld",&a)
#define sff(a,b) scanf("%lld %lld", &a , &b)
#define pf(a) printf("%lld\n",a)
#define pff(a,b) printf("%lld %lld\n", a , b)
#define bug printf("**!\n")
#define mem(a , b) memset(a, b ,sizeof(a))
#define front_zero(n) __builtin_clzll(n)
#define back_zero(n) __builtin_ctzll(n)
#define total_one(n) __builtin_popcount(n)
#define clean fflush(stdout)
 
//const ll mod =  (ll) 998244353;
const ll mod =  (ll) 1e9 + 7;
const ll maxn = (ll)1e8 + 5;
const int nnn = 1048590;
const int inf = numeric_limits<int>::max()-1;
//const ll INF = numeric_limits<ll>::max()-1;
const ll INF = (ll)1e18;
 
ll dx[]={0,1,0,-1};
ll dy[]={1,0,-1,0};
ll dxx[]={0,1,0,-1,1,1,-1,-1};
ll dyy[]={1,0,-1,0,1,-1,1,-1};
 
bool USACO = 0;
 
mt19937 rng(chrono::system_clock::now().time_since_epoch().count());
 
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
 
template <typename T> using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;

const ll N = 5e5 + 5;

vector < ll > a;
vector < ll > v[N];

void dfs(ll s, ll p){
    if(v[s].size() == 1) a.pb(s);
    for(auto u : v[s]){
        if(u - p){
            dfs(u, s);
        }
    }
    return;
}

void solve(){

    ll n; cin >> n;

    for(ll i = 1; i < n; i++){
        ll x, y; cin >> x >> y;
        v[x].pb(y);
        v[y].pb(x);
    }

    for(ll i = 1; i <= n; i++){
        if(v[i].size() != 1){
            dfs(i, 0);
            break;
        }
    }
    cout << (a.size() + 1)/2 << '\n';

    for(ll i = 0; i < (a.size()+1)/2; i++){
        cout << a[i] << ' ' << a[ (i + (a.size()/2))%a.size()] << '\n';
    }
  
  return;
}
 
int main() {
    
    
    #ifdef LOCAL
        freopen("in", "r", stdin);
        freopen("out", "w", stdout);
        auto start_time = clock();
    #else 
       ios_base::sync_with_stdio(0); cin.tie(NULL); cout.tie(NULL);
    #endif
 
    //pre(N);
 
    ll T = 1, CT = 0;  //cin >> T; 
 
    while(T--){

        solve();
    }
    #ifdef LOCAL
        auto end_time = clock();
        cerr<< "Execution time: "<<(end_time - start_time)*(int)1e3/CLOCKS_PER_SEC<<" ms\n";
    #endif
 
    return 0;
}

Compilation message (stderr)

net.cpp: In function 'void solve()':
net.cpp:99:21: warning: comparison of integer expressions of different signedness: 'll' {aka 'long long int'} and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   99 |     for(ll i = 0; i < (a.size()+1)/2; i++){
      |                   ~~^~~~~~~~~~~~~~~~
net.cpp: In function 'int main()':
net.cpp:119:15: warning: unused variable 'CT' [-Wunused-variable]
  119 |     ll T = 1, CT = 0;  //cin >> T;
      |               ^~

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