Submission #32316

#	Time	Username	Problem	Language	Result	Execution time	Memory
32316		dqhungdl	Network (BOI15_net)	C++14	100 / 100	766 ms	38724 KiB

net

#include <bits/stdc++.h>
using namespace std;

int n;
bool Free[500005];
vector<int> V,g[500005];

void DFS(int u)
{
    Free[u]=true;
    if(g[u].size()==1)
        V.push_back(u);
    for(int i=0;i<g[u].size();i++)
        if(Free[g[u][i]]==false)
            DFS(g[u][i]);
}

int main()
{
    //ios_base::sync_with_stdio(false);
    //freopen("NET.INP","r",stdin);
    scanf("%d",&n);
    int u,v;
    for(int i=1;i<n;i++)
    {
        scanf("%d%d",&u,&v);
        g[u].push_back(v);
        g[v].push_back(u);
    }
    DFS(1);
    int res=(V.size()+1)/2;
    printf("%d\n",res);
    for(int i=0;i<res;i++)
        if(i+V.size()/2<V.size())
            printf("%d %d\n",V[i],V[i+V.size()/2]);
}

Compilation message (stderr)

net.cpp: In function 'void DFS(int)':
net.cpp:13:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int i=0;i<g[u].size();i++)
                  ^
net.cpp: In function 'int main()':
net.cpp:22:19: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d",&n);
                   ^
net.cpp:26:28: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         scanf("%d%d",&u,&v);
                            ^

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