Submission #151229

#	Time	Username	Problem	Language	Result	Execution time	Memory
151229		Charis02	Network (BOI15_net)	C++14	100 / 100	578 ms	48664 KiB

net

#include<iostream>
#include<stdio.h>
#include<vector>
#include<cmath>
#include<queue>
#include<string.h>
#include<map>
#include<set>
#include<algorithm>
#define ll long long
#define pi pair < ll,ll >
#define mp(a,b) make_pair(a,b)
#define rep(i,a,b) for(int i = a;i < b;i++)
#define N 500004
#define INF 1e9+7

using namespace std;

ll n,a,b;
vector < vector < ll > > graph(N);
vector < ll > res;

void dfs(ll cur,ll par)
{
    if(graph[cur].size() == 1)
    {
        res.push_back(cur);
    }

    rep(i,0,graph[cur].size())
    {
        if(graph[cur][i] == par)
            continue;

        dfs(graph[cur][i],cur);
    }

    return;
}

int main()
{
    ios_base::sync_with_stdio(false);

    cin >> n;

    rep(i,0,n-1)
    {
        cin >> a >> b;
        graph[a].push_back(b);
        graph[b].push_back(a);
    }

    dfs(1,1);
    ll half = res.size()/2 + res.size()%2;
    ll sz = res.size();

    cout << half << endl;

    rep(i,0,half)
    {
        cout << res[i] << " "<< res[(i+half)%sz] << "\n";
    }

    return 0;
}

Compilation message (stderr)

net.cpp: In function 'void dfs(long long int, long long int)':
net.cpp:13:36: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
 #define rep(i,a,b) for(int i = a;i < b;i++)
net.cpp:30:9:
     rep(i,0,graph[cur].size())
         ~~~~~~~~~~~~~~~~~~~~~       
net.cpp:30:5: note: in expansion of macro 'rep'
     rep(i,0,graph[cur].size())
     ^~~

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