Submission #24940

#	Time	Username	Problem	Language	Result	Execution time	Memory
24940		RezwanArefin01	Network (BOI15_net)	C++14	0 / 100	3 ms	13744 KiB

net

//Bismillahir Rahmanir Rahim
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<int,int> ii;
const int maxn = 500100;
vector<int> adj[maxn], lef; 
void dfs(int u, int par){
	int cnt = 0;
	for(int v : adj[u]) if(v - par){
		cnt++, dfs(v, u); 
	} 
	if(!cnt) lef.push_back(u);
}
int main(int argc, char const *argv[]) {
#ifdef LOCAL_TESTING
	freopen("in", "r", stdin);
#endif
	int n; cin>>n; 
	for(int i=0; i<n-1; i++) {
		int u, v; 
		cin>>u>>v;
		adj[u].push_back(v); 
		adj[v].push_back(u); 
	}
	dfs(1, 0);
	vector<int> a = lef; 
	lef.clear(); 
	dfs(2, 0); 
	vector<int> b = lef;
	sort(a.begin(), a.end());
	sort(b.begin(), b.end()); 
	vector<int> c;
	merge(a.begin(), a.end(), 
		b.begin(), b.end(), 
		back_inserter(c)); 
	c.erase(unique(c.begin(), c.end()), c.end());
	if(c.size() == 1) {
		cout<<1<<endl;
		cout<<c[0]<<" " << 1<<endl;
		return 0;
	} 

	cout<<(int) (c.size() + 1)/2<<endl;
	for(int i=0; i+1<c.size(); i+=2) {
		cout<<c[i]<<" " << c[i+1]<<endl;
	}
	if(c.size() & 1) {
		cout << c[0] << " " << c[c.size()-1]<<endl;
	}
} 

Compilation message (stderr)

net.cpp: In function 'int main(int, const char**)':
net.cpp:45:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0; i+1<c.size(); i+=2) {
                  ^

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