Submission #667190

#	Time	Username	Problem	Language	Result	Execution time	Memory
667190		ktkerem	Network (BOI15_net)	C++17	100 / 100	584 ms	59520 KiB

net

/*#pragma GCC target ("avx2")
#pragma GCC optimize ("O3")
#pragma GCC optimize("Ofast")
#pragma GCC optimize ("unroll-loops")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")/**/
#include<bits/stdc++.h>
/**/
//typedef int ll;
typedef long long ll;
typedef unsigned long long ull;
typedef std::string str;
//typedef vector<std::vector<ll>> vv; 
/*typedef __int128 vll;
typedef unsigned __int128 uvll;*/
#define llll std::pair<ll , ll>
#define pb push_back
#define pf push_front
#define halo cout << "hello\n"
#define fi first
#define sec second
#define vv(x) std::vector<std::vector<x>>
#define all(a) a.begin() , a.end()
const ll limit = 1e9+7; 
const ll ous = 5e5 + 7;
const ll dx[4] = {-1 , 0 , 1 , 0} , dy[4] = {0,1,0,-1};
template <typename T> std::string type_name();
ll n , m;std::vector<ll> ar;
std::vector<ll> adj[ous] , lc(ous) , v;
ll cnt = 0;
ll finlevcnt(ll crt , ll prv = 0 , ll crp = 0){
    for(auto j:adj[crt]){
        if(j != prv){
            ll o = finlevcnt(j , crt , lc[crt] - lc[j] + crp);
            if(o){
                return o;
            }
        }
    }
    if(adj[crt].size() < 2){
        return 0;
    }
    ll kd = (cnt + 1)/2 >= crp;
    for(auto j:adj[crt]){
        if(kd == 0){
            break;
        }
        if(j != prv){
            if(lc[j] > (cnt + 1)/2){
                kd =0;
            }
        }
    }
    //std::cout << crt << " " << crp << " " << lc[3] << " " << kd << "\n";
    return(kd ?crt :0);
}
ll dfs(ll crt , ll prv){
    ll k = 1;
    for(auto j:adj[crt]){
        if(j != prv){
            k = 0;
            lc[crt] += dfs(j , crt);
        }
    }
    if(k || adj[crt].size() < 2){
        lc[crt] += 1;
        cnt++;
    }
    return lc[crt];
}
void fndlv(ll crt , ll prv){
    if(adj[crt].size() < 2){
        v.pb(crt);
        return;
    }
    for(auto j:adj[crt]){
        if(j != prv){
            fndlv(j , crt);
        }
    }
}
void solve(){
    ll n;std::cin >> n;
    for(ll i = 0;n-1>i;i++){
        ll x , y;std::cin >> x >> y;
        adj[x].pb(y);
        adj[y].pb(x);
    }
    dfs(1 , 0);
    ll o = finlevcnt(1);
    for(auto j:adj[o]){
        fndlv(j , o);
    }
    ll tl = 0;
    //std::cout << o << "\n";
    ll ps = ((cnt + 1) / 2) * 2;
    ll ans [ps];
    for(ll i = 0;ps>i;i++){
        ans[tl] = v[i % v.size()];
        tl+=2;
        if(tl == ps){
            tl = 1;
        }
    }
    std::cout << ps / 2 << "\n";
    for(ll i = 0;ps>i;i+=2){
        std::cout << ans[i] << " " << ans[i+1] << "\n";
    }
    return;/**/
}
signed main(){
    std::ios_base::sync_with_stdio(false);std::cin.tie(NULL);
    ll t=1;
    //std::cin >> t;
    ll o = 1;
    while(t--){ 
        //cout << "Case " << o++ << ":\n";
        solve();
    }
    return 0;
}/**/

Compilation message (stderr)

net.cpp:5:78: warning: "/*" within comment [-Wcomment]
    5 | #pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")/**/
      |                                                                               
net.cpp: In function 'int main()':
net.cpp:114:8: warning: unused variable 'o' [-Wunused-variable]
  114 |     ll o = 1;
      |        ^

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