Submission #209546

#	Time	Username	Problem	Language	Result	Execution time	Memory
209546		DodgeBallMan	Network (BOI15_net)	C++14	100 / 100	580 ms	47732 KiB

net

#include <bits/stdc++.h>

using namespace std;

const int N = 5e5 + 10;
int n;
vector<int> g[N], lf;

void dfs( int u, int p ) { if( g[u].size() == 1 ) lf.emplace_back( u ); for( int v : g[u] ) if( v != p ) dfs( v, u ); }

int main()
{
    scanf("%d",&n);
    for( int i = 1, a, b ; i < n ; i++ ) {
        scanf("%d %d",&a,&b);
        g[a].emplace_back( b ), g[b].emplace_back( a );
    }
    dfs( 1, 0 );
    printf("%d\n",lf.size()/2 + ( lf.size() % 2 ) );
    for( int i = 0 ; i < lf.size()/2 ; i++ ) printf("%d %d\n",lf[i],lf[i+(lf.size()/2)]);
    if( lf.size() % 2 ) printf("%d %d\n",lf[0],lf[lf.size()-1]);
    return 0;
}

Compilation message (stderr)

net.cpp: In function 'int main()':
net.cpp:19:51: warning: format '%d' expects argument of type 'int', but argument 2 has type 'std::vector<int>::size_type {aka long unsigned int}' [-Wformat=]
     printf("%d\n",lf.size()/2 + ( lf.size() % 2 ) );
                   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ^
net.cpp:20:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for( int i = 0 ; i < lf.size()/2 ; i++ ) printf("%d %d\n",lf[i],lf[i+(lf.size()/2)]);
                      ~~^~~~~~~~~~~~~
net.cpp:13:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d",&n);
     ~~~~~^~~~~~~~~
net.cpp:15:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         scanf("%d %d",&a,&b);
         ~~~~~^~~~~~~~~~~~~~~

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