Submission #887500

#	Time	Username	Problem	Language	Result	Execution time	Memory
887500		Mher777	Network (BOI15_net)	C++17	100 / 100	338 ms	48012 KiB

net

/* ----------------------------- Mher777 ----------------------------- */
#define _CRT_SECURE_NO_WARNINGS
#include <iostream>
#include <iomanip>
#include <array>
#include <string>
#include <algorithm>
#include <cmath>
#include <set>
#include <map>
#include <unordered_set>
#include <unordered_map>
#include <vector>
#include <stack>
#include <queue>
#include <deque>
#include <bitset>
#include <list>
#include <iterator>
#include <numeric>
#include <complex>
#include <utility>
#include <random>
#include <fstream>
#include <cassert>
using namespace std;

/* -------------------- Typedefs -------------------- */

typedef int itn;
typedef long long ll;
typedef unsigned long long ull;
typedef float fl;
typedef double db;
typedef long double ld;

/* -------------------- Usings -------------------- */

using vi = vector<int>;
using vll = vector<ll>;
using mii = map<int, int>;
using mll = map<ll, ll>;
using pii = pair<int, int>;
using pll = pair<ll, ll>;

/* -------------------- Defines -------------------- */

#define kap map
#define ff first
#define ss second
#define pub push_back
#define pob pop_back
#define puf push_front
#define pof pop_front
#define mpr make_pair
#define yes cout<<"YES\n"
#define no cout<<"NO\n"
#define all(x) (x).begin(), (x).end()

/* -------------------- Constants -------------------- */

const int MAX = int(1e9 + 5);
const ll MAXL = ll(1e18 + 5);
const ll MOD = ll(1e9 + 7);
const ll MOD2 = ll(998244353);
const ll CON = (ll)(911382323);
const ll MOD3 = (ll)(972663749);

/* -------------------- Functions -------------------- */

void fastio() {
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
}

void precision(int x) {
    cout.setf(ios::fixed | ios::showpoint);
    cout.precision(x);
}

ll gcd(ll a, ll b) {
    while (b) {
        a %= b;
        swap(a, b);
    }
    return a;
}

ll lcm(ll a, ll b) {
    return a / gcd(a, b) * b;
}

ll range_sum(ll a, ll b) {
    ll dif = a - 1, cnt = b - a + 1;
    ll ans = ((b - a + 1) * (b - a + 2)) / 2;
    ans += ((b - a + 1) * dif);
    return ans;
}

string dec_to_bin(ll a) {
    string s = "";
    for (ll i = a; i > 0; ) {
        ll k = i % 2;
        i /= 2;
        char c = k + 48;
        s += c;
    }
    if (a == 0) {
        s = "0";
    }
    reverse(all(s));
    return s;
}

ll bin_to_dec(string s) {
    ll num = 0;
    for (int i = 0; i < s.size(); i++) {
        num *= 2ll;
        num += (s[i] - '0');
    }
    return num;
}

int isPrime(ll a) {
    if (a == 1) return 0;
    for (ll i = 2; i * i <= a; i++) {
        if (a % i == 0) return 0;
    }
    return 1;
}

ll binpow(ll a, ll b) {
    if (!a) return 0;
    ll ans = 1;
    while (b) {
        if (b & 1) {
            ans *= a;
        }
        b >>= 1;
        a *= a;
    }
    return ans;
}

ll binpow_by_mod(ll a, ll b, ll mod) {
    if (!a) return 0;
    ll ans = 1;
    while (b) {
        if (b & 1) {
            ans *= a;
            ans %= mod;
        }
        b >>= 1;
        a *= a;
        a %= mod;
    }
    return ans;
}

/* -------------------- Solution -------------------- */

const int N = 500005;
vi g[N];
vi root;

void dfs(int u = 1, int p = 0) {
    if (g[u].size() == 1) root.pub(u);
    for (auto to : g[u]) {
        if (to != p) dfs(to, u);
    }
}

void slv() {
    int n;
    cin >> n;
    for (int i = 0; i < n - 1; ++i) {
        int x, y;
        cin >> x >> y;
        g[x].pub(y);
        g[y].pub(x);
    }
    dfs();
    int answ = root.size() / 2;
    vector<pii> ans;
    for (int i = 0; i < answ; ++i) {
        ans.pub({ root[i],root[i + answ] });
    }
    if (root.size() % 2) ans.pub({ root[0],root.back() }), ++answ;
    cout << answ << '\n';
    for (auto elem : ans) {
        cout << elem.ff << " " << elem.ss << '\n';
    }
}

void cs() {
    int tstc = 1;
    //cin >> tstc;
    while (tstc--) {
        slv();
    }
}

void precalc() {
    return;
}

int main() {
    fastio();
    precalc();
    //precision(0);
    cs();
    return 0;
}

Compilation message (stderr)

net.cpp: In function 'll range_sum(ll, ll)':
net.cpp:95:21: warning: unused variable 'cnt' [-Wunused-variable]
   95 |     ll dif = a - 1, cnt = b - a + 1;
      |                     ^~~
net.cpp: In function 'll bin_to_dec(std::string)':
net.cpp:118:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  118 |     for (int i = 0; i < s.size(); i++) {
      |                     ~~^~~~~~~~~~

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