Submission #764945

#	Time	Username	Problem	Language	Result	Execution time	Memory
764945		vjudge1	Network (BOI15_net)	C++17	0 / 100	3 ms	5028 KiB

net

/******************
tree-bends-in-youth
//22///06///2023///
******************/
#include <bits/stdc++.h>
#define ll long long
#define F first
#define S second
#define pb push_back
#define all(x) x.begin(), x.end()
using namespace std;
const ll N = 2e5 + 1;
const ll INF = 1e17;
const ll MOD = 1e9 + 7;
vector <int> g[N];
map <int,int> used;
int d[N];
void solve(){
    int n;
    cin >> n;
    set <int> s;
    for(int i = 1;i <= n;i++){
        s.insert(i);
    }
    for(int i = 1;i < n;i++){
        int x,y;
        cin >> x >> y;
        g[x].pb(y);
        g[y].pb(x);
        if(g[x].size() > 1)s.erase(x);
        if(g[y].size() > 1)s.erase(y);
    }
    vector <int> a;
    for(auto to : s){
        a.pb(to);
    }
    cout << ((a.size() + 1) / 2) << '\n';
    for(int i = 0;i < a.size();i++){
        if(s.count(a[i]) == 0)continue;
        s.erase(a[i]);
        cout << a[i] << " ";
        if(s.empty()){
            cout << a[i-  1] << '\n';
            continue;
        }
        for(int j = 1;j <= n;j++){
            d[j] = 0;
        }
        queue <int> q;
        q.push(a[i]);
        used.clear();
        used[a[i]] = 1;
        while(!q.empty()){
            int v=  q.front();
            q.pop();
            for(auto to : g[v]){
                if(used[to] == 0){
                    q.push(to);
                    used[to] = 1;
                    d[to] = d[v] + 1;
                }
            }
        }
        int mx = 0,w = 0;
        for(auto to : s){
            if(d[to] > mx){
                mx = d[to];
                w = to;
            }
        }
        cout << w << "\n";
        s.erase(w);
    }
}
main () {
    ios_base::sync_with_stdio(0);
    cin.tie(0);
	//freopen("censor.in","r",stdin);
	//freopen("censor.out","w",stdout);
    ll T = 1;
    //cin >> T;
    for(ll i = 1;i <= T;i++){
      //  cout << "Case " << i << ":\n";
        solve();
    }
}

Compilation message (stderr)

net.cpp: In function 'void solve()':
net.cpp:38:21: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   38 |     for(int i = 0;i < a.size();i++){
      |                   ~~^~~~~~~~~~
net.cpp: At global scope:
net.cpp:75:1: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
   75 | main () {
      | ^~~~

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