Submission #660665

#	Time	Username	Problem	Language	Result	Execution time	Memory
660665		Lobo	Spring cleaning (CEOI20_cleaning)	C++17	28 / 100	1077 ms	11156 KiB

cleaning

#include<bits/stdc++.h>
using namespace std;
const long long inf = (long long) 1e18 + 10;
const int inf1 = (int) 1e9 + 10;
// #define int long long
#define dbl long double
#define endl '\n'
#define sc second
#define fr first
#define mp make_pair
#define pb push_back
#define all(x) x.begin(), x.end()

const int maxn = 1e5+10;

int n, q, gr[maxn], p[maxn], sbl[maxn];
vector<int> g[maxn];
int cntl, ans;

void dfs(int u, int ant) {
    p[u] = ant;
    if(gr[u] == 1) {
        cntl++;
        sbl[u] = 1;
    }
    else sbl[u] = 0;
    for(auto v : g[u]) if(v != ant) {
        dfs(v,u);
        sbl[u]^= sbl[v];
    }
}

void change(int v) {
    while(v != -1) {
        if(sbl[v] == 1) ans--;
        sbl[v]^= 1;
        if(sbl[v] == 1) ans++;
        v = p[v];
    }
}

void solve() {
    cin >> n >> q;
    for(int i = 1; i <= n-1; i++) {
        int u,v; cin >> u >> v;
        g[u].pb(v);
        g[v].pb(u);
        gr[u]++;
        gr[v]++;
    }

    int rt;
    for(int i = 1; i <= n; i++) {
        if(gr[i] != 1) {
            rt = i;
            break;
        }
    }
    dfs(rt,-1);

    for(int i = 1; i <= n; i++) {
        if(sbl[i] == 1) ans++;
    }

    while(q--) {
        int D; cin >> D;
        vector<int> as;
        for(int i = 0; i < D; i++) {
            int v; cin >> v;
            as.pb(v);

            if(gr[v] == 1) {
                cntl--;
                change(v);
            }
            gr[v]++;
            cntl++;
            change(v);
        }

        // for(int i = 1; i <= n; i++) {
        //     cout << i << " " << sbl[i] << endl;
        // }
        // cout << ans << endl;

        if(cntl%2 == 1) {
            cout << -1 << endl;
        }
        else {
            int q1 = ans+D;
            int q2 = n-1-ans;
            cout << q1 + 2*q2 << endl;
        }

        for(int i = 0; i < D; i++) {
            int v = as[i];
            gr[v]--;
            if(gr[v] == 1) {
                cntl++;
                change(v);
            }
            cntl--;
            change(v);
        }

    }
}

int32_t main() {
    ios::sync_with_stdio(false); cin.tie(0);

    // freopen("in.in", "r", stdin);
    // freopen("out.out", "w", stdout);
    int tt = 1;
    // cin >> tt;
    while(tt--) {
        solve();
    }

}

Compilation message (stderr)

cleaning.cpp: In function 'void solve()':
cleaning.cpp:59:8: warning: 'rt' may be used uninitialized in this function [-Wmaybe-uninitialized]
   59 |     dfs(rt,-1);
      |     ~~~^~~~~~~

• Subtask 1: 0 / 0
• Subtask 2: 9 / 9
• Subtask 3: 0 / 9
• Subtask 4: 0 / 16
• Subtask 5: 19 / 19
• Subtask 6: 0 / 17
• Subtask 7: 0 / 30