Submission #1272063

#	Time	Username	Problem	Language	Result	Execution time	Memory
1272063		thesen	Logičari (COCI21_logicari)	C++20	10 / 110	25 ms	6044 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;

bool dfs(vector<vll> &path, vll &col, ll x, ll prev, ll k){
    //cout << x << ' ' << prev << ' ' << k << endl;
    k++;
    //cout << x << ' ' << prev << ' ' << k << endl;
    if(col[x] == 0)col[x] = k;
    else if(col[x] != k)return false;
    else return true;
    for(ll i : path[x]){
        if(i == prev)continue;
        //cout << i <<',';
        if(col[i] == 0)col[i] = k;
        else if(col[i] != k)return false;
        else return true;
        //cout << i << ' ';
        for(ll j : path[i]){
            if(j == x)continue;
            if(!dfs(path, col, j, i, k%2))return false;
        }
    }//cout << endl;
    return true;
}

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 res = -1;
    for(ll i : path[a]){
        vll col(n+1); col[a] = col[b] = col[i] = 2;
        bool ans = true;
        for(ll j : path[a]){
            if(j == i)continue;
            if(!dfs(path, col, j, a, 0))ans = false;
        }
        for(ll j : path[i]){
            if(j == a)continue;
            if(!dfs(path, col, j, i, 0))ans = false;
        }
        //cout << a << ' ' << i << endl;
        //for(ll t = 1; t <= n; t++)cout << col[t] << ' ';
        //cout << endl;
        if(ans){
            ll tot = 0;
            for(ll i = 1; i <= n; i++){
                if(col[i] == 2)tot++;
            }
            if(res == -1)res = tot;
            else res = min(res, tot);
        }
    }cout << res << 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