Submission #1053598

#	Time	Username	Problem	Language	Result	Execution time	Memory
1053598		Ejen	Mousetrap (CEOI17_mousetrap)	C++14	20 / 100	439 ms	83280 KiB

mousetrap

#include <bits/stdc++.h>

#define el '\n'
#define fu(i, a, b) for (long long i = a; i <= b; ++i)
#define fd(i, a, b) for (long long i = a; i >= b; --i)
#define ff first
#define ss second
#define all(v) v.begin(), v.end()
#define sz(v)  (ll)v.size()
#define mask(i) (1LL << i)
#define bit(x, i) ((x) >> (i) & 1)

using namespace std;
typedef int ll;
typedef unsigned long long ull;

mt19937_64 rng(chrono::high_resolution_clock::now().time_since_epoch().count());

ll Rand(ll l, ll r) {
    return uniform_int_distribution<ll> (l, r) (rng);
}

ll last(ll msk)    {return msk & (-msk);}
ll pop_cnt(ll msk) {return __builtin_popcountll(msk);}
ll ctz(ll msk)     {return __builtin_ctzll(msk);}
ll lg(ll msk)      {return 63 - __builtin_clzll(msk);}

template<class T1, class T2>
    bool maximize(T1 &a, T2 b) {
        if (a < b) {
            a = b;
            return true;
        }
        return false;
    }

template<class T1, class T2>
    bool minimize(T1 &a, T2 b) {
        if (a > b) {
            a = b;
            return true;
        }
        return false;
    }

template<class T>
    void print(T &a, string sep = " ", string stop = "\n") {
        for (auto x : a) cout << x << sep;
        cout << stop;
    }

template<class T>
    void compress(vector<T> &v) {
        sort(all(v));
        v.resize(unique(all(v)) - v.begin());
    }

const long long N = 1e6 + 27, base = 311, inf = 2e18, mod = 1e9 + 19972207;

ll n, t, m, timer, cur;
ll a[N], f[N], in[N], out[N], left[N];
vector<ll> adj[N];

void dfs(ll u, ll p) {
    in[u] = ++timer;
    vector<ll> tmp;
    for (ll v : adj[u]) {
        if (v == p) continue;
        dfs(v, u);
        if (u == t) {
            if (in[v] <= in[m] && in[m] <= out[v]) {
                cout << f[v];
                exit(0);
            }
        }
        f[u] += f[v];
        if (in[v] > in[m] || in[m] > out[v]) {
            f[u]++;
            tmp.push_back(f[v]);
        }
    }
    out[u] = timer;
    if (in[u] <= in[m] && in[m] <= out[u] && tmp.empty()) cur++;
    sort(all(tmp));
    if (sz(tmp)) f[u] -= tmp.back();
    fd(i, sz(tmp) - 2, 0) {
        if (!cur) break;
        cur--;
        f[u] -= tmp[i];
    }
    
}

signed main() {
    // freopen("brentford40mu.inp", "r", stdin);
    // freopen("brentford40mu.out", "w", stdout);
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    cin >> n >> t >> m;
    if (t == m) return cout << 0, 0;
    fu(i, 2, n) {
        ll u, v;
        cin >> u >> v;
        adj[u].push_back(v);
        adj[v].push_back(u);
    }
    dfs(t, 0);
    // fu(i, 1, n) cout << f[i] << ' ';
    // cout << f[t];
}

• Subtask 1: 20 / 20
• Subtask 2: 0 / 25
• Subtask 3: 0 / 20
• Subtask 4: 0 / 35