Submission #394763

#	Time	Username	Problem	Language	Result	Execution time	Memory
394763		MHNaderi	Network (BOI15_net)	C++14	100 / 100	501 ms	45684 KiB

net

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

using namespace std;
using namespace __gnu_pbds;
#define ordered_set tree<int, null_type,less<int>, rb_tree_tag,tree_order_statistics_node_update>
//#define int long long
#define pb push_back
#define pii pair<int,int>
#define F first
#define S second
const int maxn=5e5+7;
int n;
vector<int> adj[maxn];
void preprocess(){
    cin>>n;
    for(int i=1;i<n;i++){
        int u,v;
        cin>>u>>v;
        adj[u].pb(v);
        adj[v].pb(u);
    }
}
vector<int> ans;
void dfs(int u,int p){
    for(auto v : adj[u])
        if(v != p)
            dfs(v,u);
    if(adj[u].size() == 1)
        ans.pb(u);
}
void process(){
    dfs(1,1);
}
void afterprocess(){
    int javab=ans.size()/2;
    cout<<javab+(ans.size()%2)<<'\n';
    for(int i=0;i<javab;i++)
        cout<<ans[i]<<' '<<ans[i+javab]<<'\n';
    if(ans.size()%2)
        cout<<ans[2*javab]<<' '<<ans[0]<<'\n';
}
int32_t main(){
	ios_base::sync_with_stdio(0);
	preprocess();process();afterprocess();

	return 0;
}

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