Submission #641295

#	Time	Username	Problem	Language	Result	Execution time	Memory
641295		ghostwriter	Network (BOI15_net)	C++14	100 / 100	543 ms	94520 KiB

net

#include <bits/stdc++.h>
using namespace std;
#ifdef LOCAL
#include <debug.h>
#endif
#define st first
#define nd second
#define pb push_back
#define pf push_front
#define _pb pop_back
#define _pf pop_front
#define lb lower_bound
#define ub upper_bound
#define mtp make_tuple
#define all(x) (x).begin(), (x).end()
#define sz(x) (int)(x).size()
typedef long long ll; typedef unsigned long long ull;
typedef double db; typedef long double ldb;
typedef pair<int, int> pi; typedef pair<ll, ll> pll;
typedef vector<int> vi; typedef vector<ll> vll; typedef vector<pi> vpi; typedef vector<pll> vpll;
typedef string str;
template<typename T> T gcd(T a, T b) { return (b == 0? a : gcd(b, a % b)); }
template<typename T> T lcm(T a, T b) { return a / gcd(a, b) * b; }
#define FOR(i, l, r) for (int (i) = (l); (i) <= (r); ++(i))
#define FOS(i, r, l) for (int (i) = (r); (i) >= (l); --(i))
#define EACH(i, x) for (auto &(i) : (x))
#define WHILE while
#define file "TEST"
mt19937 rd(chrono::steady_clock::now().time_since_epoch().count());
ll rand(ll l, ll r) { return uniform_int_distribution<ll>(l, r)(rd); }
/*
    Tran The Bao
    CTL - Da Lat
    Cay ngay cay dem nhung deo duoc cong nhan
*/
const int N = 5e5 + 5;
int n, root, cntl[N], cnt = 0;
vi adj[N], a[N], leafs;
vpi ans;
multiset<pi, greater<pi> > s;
void dfs(int u, int p) {
	EACH(v, adj[u]) {
		if (v == p) continue;
		dfs(v, u);
		cntl[u] += cntl[v];
	}
	if (sz(adj[u]) == 1) {
		leafs.pb(u);
		cntl[u] = 1;
	}
}
int fct(int u, int p, int s) {
	EACH(v, adj[u]) {
		if (v == p || sz(adj[v]) == 1) continue;
		if (cntl[v] > s / 2) return fct(v, u, s);
	}
	return u;
}
void dfs1(int u, int p) {
	EACH(v, adj[u]) {
		if (v == p) continue;
		if (u == root) ++cnt;
		dfs1(v, u);
	}
	if (sz(adj[u]) == 1) a[cnt].pb(u);
}
signed main() {
    ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0);
    // freopen(file".inp", "r", stdin);
    // freopen(file".out", "w", stdout);
    cin >> n;
    FOR(i, 1, n - 1) {
    	int u, v;
    	cin >> u >> v;
    	adj[u].pb(v);
    	adj[v].pb(u);
    }
    FOR(i, 1, n)
    	if (sz(adj[i]) > 1)
    		root = i;
    dfs(root, 0);
    root = fct(root, 0, cntl[root]);
    dfs1(root, 0);
    FOR(i, 1, cnt) s.insert({sz(a[i]), i});
    WHILE(sz(s) > 1) {
    	int u = (*s.begin()).nd, v = (*++s.begin()).nd;
    	s.erase(s.begin());
    	s.erase(s.begin());
    	ans.pb({a[u].back(), a[v].back()});
    	a[u]._pb();
    	a[v]._pb();
    	if (!a[u].empty()) s.insert({sz(a[u]), u});
    	if (!a[v].empty()) s.insert({sz(a[v]), v});
    }
    if (!s.empty()) {
    	int u = a[(*s.begin()).nd].back();
    	ans.pb({u, u == leafs[0]? leafs[1] : leafs[0]});
    }
    cout << sz(ans) << '\n';
    EACH(i, ans) cout << i.st << ' ' << i.nd << '\n';
    return 0;
}
/*
9
2 1
3 2
4 3
5 4
6 2
7 5
8 5
9 7
*/

Compilation message (stderr)

net.cpp: In function 'void dfs(int, int)':
net.cpp:26:31: warning: unnecessary parentheses in declaration of 'v' [-Wparentheses]
   26 | #define EACH(i, x) for (auto &(i) : (x))
      |                               ^
net.cpp:42:2: note: in expansion of macro 'EACH'
   42 |  EACH(v, adj[u]) {
      |  ^~~~
net.cpp: In function 'int fct(int, int, int)':
net.cpp:26:31: warning: unnecessary parentheses in declaration of 'v' [-Wparentheses]
   26 | #define EACH(i, x) for (auto &(i) : (x))
      |                               ^
net.cpp:53:2: note: in expansion of macro 'EACH'
   53 |  EACH(v, adj[u]) {
      |  ^~~~
net.cpp: In function 'void dfs1(int, int)':
net.cpp:26:31: warning: unnecessary parentheses in declaration of 'v' [-Wparentheses]
   26 | #define EACH(i, x) for (auto &(i) : (x))
      |                               ^
net.cpp:60:2: note: in expansion of macro 'EACH'
   60 |  EACH(v, adj[u]) {
      |  ^~~~
net.cpp: In function 'int main()':
net.cpp:24:31: warning: unnecessary parentheses in declaration of 'i' [-Wparentheses]
   24 | #define FOR(i, l, r) for (int (i) = (l); (i) <= (r); ++(i))
      |                               ^
net.cpp:72:5: note: in expansion of macro 'FOR'
   72 |     FOR(i, 1, n - 1) {
      |     ^~~
net.cpp:24:31: warning: unnecessary parentheses in declaration of 'i' [-Wparentheses]
   24 | #define FOR(i, l, r) for (int (i) = (l); (i) <= (r); ++(i))
      |                               ^
net.cpp:78:5: note: in expansion of macro 'FOR'
   78 |     FOR(i, 1, n)
      |     ^~~
net.cpp:24:31: warning: unnecessary parentheses in declaration of 'i' [-Wparentheses]
   24 | #define FOR(i, l, r) for (int (i) = (l); (i) <= (r); ++(i))
      |                               ^
net.cpp:84:5: note: in expansion of macro 'FOR'
   84 |     FOR(i, 1, cnt) s.insert({sz(a[i]), i});
      |     ^~~
net.cpp:26:31: warning: unnecessary parentheses in declaration of 'i' [-Wparentheses]
   26 | #define EACH(i, x) for (auto &(i) : (x))
      |                               ^
net.cpp:100:5: note: in expansion of macro 'EACH'
  100 |     EACH(i, ans) cout << i.st << ' ' << i.nd << '\n';
      |     ^~~~

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