Submission #93779

#	Time	Username	Problem	Language	Result	Execution time	Memory
93779		kjain_1810	Network (BOI15_net)	C++11	63 / 100	7 ms	5240 KiB

net

#include <bits/stdc++.h>
#define pb push_back
#define f first
#define s second
#define ind(a) scanf("%d", &a)
#define inlld(a) scanf("%lld", &a)
#define ind2(a, b) scanf("%d%d", &a, &b)
#define inlld2(a, b) scanf("%lld%lld", &a, &b)
#define ind3(a, b, c) scanf("%d%d%d", &a, &b, &c)
#define inlld3(a, b, c) scanf("%lld%lld%lld", &a, &b, &c)

using namespace std;

const int N=1e5+5;
const int MOD=1e9+7;

typedef long long ll;
typedef long double ld;

ll n;
vector<ll>adj[N], leaf, nonleaf;

void dfs(ll u, ll p)
{
    if(adj[u].size()==1)
        leaf.pb(u);
    else
        nonleaf.pb(u);
    for(auto v:adj[u])
        if(v!=p)
            dfs(v, u);
}

int main() 
{
    inlld(n);
    for(ll a=1; a<n; a++)
    {
        ll u, v;
        inlld2(u, v);
        adj[u].pb(v);
        adj[v].pb(u);
    }
    for(ll a=1; a<=n; a++)
        if(adj[a].size()>1)
        {
            dfs(a, 0);
            break;
        }
    ll ans=((int)leaf.size()+1)/2;
    printf("%lld\n", ans);
    for(ll a=0; a*2+1<leaf.size(); a++)
        printf("%lld %lld\n", leaf[a], leaf[a+(leaf.size()+1)/2]);
    if(leaf.size()%2==1)
        printf("%lld %lld\n", leaf[leaf.size()/2], leaf[0]);
    return 0;
}

Compilation message (stderr)

net.cpp: In function 'int main()':
net.cpp:52:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(ll a=0; a*2+1<leaf.size(); a++)
                 ~~~~~^~~~~~~~~~~~
net.cpp:6:23: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
 #define inlld(a) scanf("%lld", &a)
                  ~~~~~^~~~~~~~~~~~
net.cpp:36:5: note: in expansion of macro 'inlld'
     inlld(n);
     ^~~~~
net.cpp:8:27: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
 #define inlld2(a, b) scanf("%lld%lld", &a, &b)
                      ~~~~~^~~~~~~~~~~~~~~~~~~~
net.cpp:40:9: note: in expansion of macro 'inlld2'
         inlld2(u, v);
         ^~~~~~

• Subtask 1: 18 / 18
• Subtask 2: 45 / 45
• Subtask 3: 0 / 37