Submission #226273

#	Time	Username	Problem	Language	Result	Execution time	Memory
226273		MKopchev	Network (BOI15_net)	C++14	100 / 100	519 ms	45300 KiB

net

#include<bits/stdc++.h>
using namespace std;
const int nmax=5e5+42;

int n;
vector<int> adj[nmax];

vector<int> leaves;

void dfs(int node,int par)
{
    if(adj[node].size()==1)leaves.push_back(node);

    for(auto k:adj[node])
        if(k!=par)dfs(k,node);
}
int main()
{
    scanf("%i",&n);

    int u,v;
    for(int i=1;i<n;i++)
    {
        scanf("%i%i",&u,&v);
        adj[u].push_back(v);
        adj[v].push_back(u);
    }

    for(int i=1;i<=n;i++)
        if(adj[i].size()>=2)
        {
            dfs(i,0);
            break;
        }

    int output=(leaves.size()+1)/2;
    printf("%i\n",output);

    int step=leaves.size()-output;

    for(int i=0;i<output;i++)
    {
        printf("%i %i\n",leaves[i],leaves[i+step]);
    }

    return 0;
}

Compilation message (stderr)

net.cpp: In function 'int main()':
net.cpp:19:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%i",&n);
     ~~~~~^~~~~~~~~
net.cpp:24:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         scanf("%i%i",&u,&v);
         ~~~~~^~~~~~~~~~~~~~

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