Submission #58618

#	Time	Username	Problem	Language	Result	Execution time	Memory
58618		SpeedOfMagic	Network (BOI15_net)	C++17	0 / 100	16 ms	12620 KiB

net

/** MIT License Copyright (c) 2018 Vasilyev Daniil **/
#include <bits/stdc++.h>
using namespace std;
#pragma GCC optimize("Ofast")
template<typename T> using v = vector<T>;
#define int long long
typedef string str;
typedef vector<int> vint;
#define rep(a, l, r) for(int a = (l); a < (r); a++)
#define pb push_back
#define sz(a) ((int) a.size())
const long long inf = 4611686018427387903; //2^62 - 1
#if 0  //FileIO
const string fileName = "";
ifstream fin ((fileName == "" ? "input.txt"  : fileName + ".in" ));
ofstream fout((fileName == "" ? "output.txt" : fileName + ".out"));
#define get fin>>
#define put fout<<
#else
#define get cin>>
#define put cout<<
#endif
#define eol put endl
void read() {}     template<typename Arg,typename... Args> void read (Arg& arg,Args&... args){get (arg)     ;read(args...) ;}
void print(){}     template<typename Arg,typename... Args> void print(Arg  arg,Args...  args){put (arg)<<" ";print(args...);}
void debug(){eol;} template<typename Arg,typename... Args> void debug(Arg  arg,Args...  args){put (arg)<<" ";debug(args...);}
int getInt(){int a; get a; return a;}
//code goes here
const int N = 5e5 + 1;
v<pair<int, int>> leaves;
vint g[N];
void dfs(int cur = 1, int p = -1, int h = 0) {
    if (sz(g[cur]) == 1)
        leaves.pb({h, cur});
    for (int i : g[cur])
        if (i != p)
            dfs(i, cur, h + 1);
}
void run() {
    int n;
    get n;
    n++;
    rep(i, 2, n) {
        int v, u;
        read(v, u);
        g[v].pb(u);
        g[u].pb(v);
    }
    dfs();

    put sz(leaves) / 2 + sz(leaves) % 2;
    eol;

    sort(leaves.begin(), leaves.end());

    int p1 = 0, p2 = sz(leaves) - 1;
    while (p1 < p2) {
        print(leaves[p1].second, leaves[p2].second);
        eol;
        p1++;
        p2--;
    }

    if (sz(leaves) % 2) {
        print(leaves[p1].second);
        rep(i, 1, n)
            if (leaves[p1].second != i && g[leaves[p1].second][0] != i) {
                print(i);
                eol;
                return;
            }
    }
}

int32_t main() {srand(time(0)); ios::sync_with_stdio(0); cin.tie(0); cout.tie(0); put fixed; put setprecision(15); run(); return 0;}

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