Submission #51613

#	Time	Username	Problem	Language	Result	Execution time	Memory
51613		okaybody10	Network (BOI15_net)	C++98	100 / 100	673 ms	155376 KiB

net

#include <bits/stdc++.h>
using namespace std;
vector<int> v[600005],ans;
void dfs(int e,int s)
{
    if(v[e].size()==1) { ans.push_back(e); return; }
    int sz=v[e].size();
    for(int i=0;i<sz;i++)
    {
        if(v[e][i]==s) continue;
        dfs(v[e][i],e);
    }
}
int main()
{
    int n; scanf("%d",&n);
    for(int i=0;i<n-1;i++)
    {
        int x,y; scanf("%d %d",&x,&y);
        v[x].push_back(y);
        v[y].push_back(x);
    }
    int firstdfs;
    for(int i=1;i<=n;i++) if(v[i].size()>=2) { firstdfs=i; break;}
    dfs(firstdfs,-1);
    int sz=ans.size();
    printf("%d\n",sz/2+sz%2);
    for(int i=0;i+sz/2<sz;i++) printf("%d %d\n",ans[i],ans[i+sz/2]);
    return 0;
}

Compilation message (stderr)

net.cpp: In function 'int main()':
net.cpp:16:17: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     int n; scanf("%d",&n);
            ~~~~~^~~~~~~~~
net.cpp:19:23: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         int x,y; scanf("%d %d",&x,&y);
                  ~~~~~^~~~~~~~~~~~~~~
net.cpp:25:8: warning: 'firstdfs' may be used uninitialized in this function [-Wmaybe-uninitialized]
     dfs(firstdfs,-1);
     ~~~^~~~~~~~~~~~~

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