Submission #1272069

#	Time	Username	Problem	Language	Result	Execution time	Memory
1272069		thesen	Logičari (COCI21_logicari)	C++20	10 / 110	22 ms	5916 KiB

Main

#include <bits/stdc++.h>
#define pb push_back
#define ll long long
#define vll vector <ll>
#define vbool vector<bool>
#define pairll pair<ll,ll>
#define fi first
#define sc second
#define rever greater<ll>()
using namespace std;

ll res = 0;
void dfs(vector<vll> &path, vll &par, vbool &vis, ll x){
    if(vis[x])return;
    vis[x] = true;
    bool ans = 1;
    for(ll j : path[x]){
        if(par[j] != 0 && par[j] != x){ans = false; break;}
    }
    if(ans){
        res++;
        for(ll j : path[x])par[j] = x;
    }
    for(ll j : path[x])dfs(path, par, vis, j);
}

void solve(){
    ll n; cin >> n;

    vector<vll> path(n+1);
    for(ll i = 0, u, v; i < n; i++){
        cin >> u >> v;
        path[u].pb(v); path[v].pb(u);
    }

    ll a = 0, b = 0;
    for(ll i = 1; i <= n; i++){
        if(path[i].size() == 1){
            if(a)b = i;
            else a = i;
        }
    }
    if(a == 0){
        if(n%4)cout << -1 << endl;
        else cout << n/2 << endl;
        return;
    }

    if(a)a = path[a][0];
    if(b)b = path[b][0];
    
    ll tot = -1;
    for(ll st : path[a]){
        vll par(n+1);
        for(ll i : path[a])par[i] = a;
        if(b){
            for(ll i : path[b]){
                if(par[i] != 0){
                    cout << -1 << endl; return;
                }par[i] = b;
            }
        }
        vbool vis(n+1); vis[a] = vis[b] = vis[st] = true;

        res = 1;
        if(a)res++;
        if(b)res++;
        bool ans = true;
        for(ll i : path[st]){
            if(par[i]){
                ans = false; break;
            }par[i] = st;
        }
        for(ll i : path[a])dfs(path, par, vis, i);
        for(ll i : path[st])dfs(path, par, vis, st);
        if(b){
            for(ll i : path[b])dfs(path, par, vis, i);
        }
        
        for(ll i = 1; i <= n; i++){
            if(!par[i])ans = false;
        }
        if(ans){
            if(tot == -1)tot = res;
            else tot = min(tot, res);
        }
    }cout << tot << endl;
}

int main(){
    ios::sync_with_stdio(false); cin.tie(nullptr);
    ll t=1; //cin >> t;
    for(int i = 1; i <= t; i++){
        solve();
    }
}

• Subtask 1: 10 / 10
• Subtask 2: 0 / 10
• Subtask 3: 0 / 40
• Subtask 4: 0 / 50