Submission #122121

#	Time	Username	Problem	Language	Result	Execution time	Memory
122121		Gustav	Network (BOI15_net)	C++14	0 / 100	2 ms	384 KiB

net

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<int, int> pi;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef vector<vl> vvl;
typedef vector<pi> vpi;
typedef vector<vi> vvi;
const int inf = 0x3f3f3f3f;
const ll linf = 123456789012345678;
const ll mod = 998244353;
#pragma GCC optimize("Ofast")
#define all(x) x.begin(), x.end()
#define debug(x) cerr << #x << " = " << x << endl

int n;
vvi conn;

int main(){
    cin.sync_with_stdio(false);
    cin.tie(0);
    
    cin >> n;
    conn = vvi(n);
    for(int i = 0; i < n-1; i++){
        int u, v;
        cin >> u >> v;
        u--, v--;
        conn[u].push_back(v);
        conn[v].push_back(u);
    }

    vi u;
    for(int i = 0; i < n; i++) if(conn[i].size() == 1) u.push_back(i);
    cout << (u.size()+1)/2 << "\n";
    for(int i = 1; i < u.size(); i+=2) cout << u[i]+1 << " " << u[i-1]+1 << "\n";
    if(u.size()%2 == 1){
        int to = 0;
        if(u[u.size()-1] == to) to++;
        if(conn[u[u.size()-1]][0] == to) to++;
        if(u[u.size()-1] == to) to++;
        cout << u[u.size()-1]+1 << " " << to+1 << "\n";
    }
}

Compilation message (stderr)

net.cpp: In function 'int main()':
net.cpp:37:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int i = 1; i < u.size(); i+=2) cout << u[i]+1 << " " << u[i-1]+1 << "\n";
                    ~~^~~~~~~~~~

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