Submission #1107412

#	Time	Username	Problem	Language	Result	Execution time	Memory
1107412		koukirocks	Network (BOI15_net)	C++17	0 / 100	1 ms	336 KiB

net

#include <bits/stdc++.h>
#define speed ios_base::sync_with_stdio(0); cin.tie(0)
#define all(x) (x).begin(),(x).end()
#define F first
#define S second
//#pragma GCC optimize("O3,unroll-loops")
//#pragma GCC target("avx,avx2")
//#pragma GCC target("popcnt")
 
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef double db;
typedef long double ldb;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
 
const ll MAX=2e5+10,P=1e9+7;
const ll INF=0x3f3f3f3f,oo=0x3f3f3f3f3f3f3f3f;
const ldb eps=1e-6;
const ldb PI=acos(-1.0);
const int dir[4][2]={{0,1},{0,-1},{1,0},{-1,0}};
template<typename T>
using vvector = vector<vector<T>>;

void dfs(int v,int p,vvector<int> &G,vector<int> &lv) {
    bool islv=true;
    for (int i:G[v]) {
        if (i==p) continue;
        islv=false;
        dfs(i,v,G,lv);
    }
    if (islv) lv.push_back(v);
}

int main() {
    speed;
    int n;
    cin>>n;
    vvector<int> G(n+1);
    for (int i=0;i<n-1;i++) {
        int a,b;
        cin>>a>>b;
        G[a].push_back(b);
        G[b].push_back(a);
    }
    int rot=0;
    for (int i=1;i<=n;i++) {
        if (G[i].size()>1) {
            rot=i;
            break;
        }
    }
    vector<int> lv;
    dfs(rot,0,G,lv);
    cout<<(lv.size()+1)/2<<"\n";
    for (int i=0;i<lv.size()/2;i++) {
        cout<<lv[2*i]<<" "<<lv[2*i+1]<<"\n";
    }
    if (lv.size()&1) cout<<lv[lv.size()-1]<<" "<<rot<<"\n";
    return 0;
}

Compilation message (stderr)

net.cpp: In function 'int main()':
net.cpp:57:19: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   57 |     for (int i=0;i<lv.size()/2;i++) {
      |                  ~^~~~~~~~~~~~

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