Submission #1127235

#	Time	Username	Problem	Language	Result	Execution time	Memory
1127235		KasymK	Network (BOI15_net)	C++20	100 / 100	418 ms	49792 KiB

net

#include "bits/stdc++.h"
using namespace std;
#define ff first
#define ss second
#define all(v) v.begin(), v.end()
#define ll long long
#define pb push_back
#define pii pair<int, int>
#define pli pair<ll, int>
#define pll pair<ll, ll>
#define tr(i, c) for(auto i = c.begin(); i != c.end(); ++i)
#define wr puts("----------------")
template<class T>bool umin(T& a,T b){if(a>b){a=b;return 1;}return 0;}
template<class T>bool umax(T& a,T b){if(a<b){a=b;return 1;}return 0;}
const int N = 5e5+5;
vector<int> adj[N], lf;

void dfs(int x=1, int pr=-1){
	tr(it, adj[x])
	if(*it!=pr)
		dfs(*it, x);
	if((int)adj[x].size()==1)
		lf.pb(x);
}

int main(){
	int n;
	scanf("%d", &n);
	for(int i = 1; i < n; ++i){
		int a, b;
		scanf("%d%d", &a, &b);
		adj[a].pb(b);
		adj[b].pb(a);
	}
	dfs();
	vector<pii> ans;
	for(int i = 0; i < ((int)lf.size()+1)/2; ++i)
		ans.pb({lf[i], lf[i+(int)lf.size()/2]});
	printf("%d\n", (int)ans.size());
	tr(it, ans)
	printf("%d %d\n", it->ff, it->ss);
	return 0;
}

Compilation message (stderr)

net.cpp: In function 'int main()':
net.cpp:28:14: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   28 |         scanf("%d", &n);
      |         ~~~~~^~~~~~~~~~
net.cpp:31:22: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   31 |                 scanf("%d%d", &a, &b);
      |                 ~~~~~^~~~~~~~~~~~~~~~

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