Submission #494999

#	Time	Username	Problem	Language	Result	Execution time	Memory
494999		Victor	Papričice (COCI20_papricice)	C++17	110 / 110	751 ms	34376 KiB

papricice

// #pragma GCC target ("avx,avx2,fma")
// #pragma GCC optimize ("Ofast,inline") // O1 - O2 - O3 - Os - Ofast
// #pragma GCC optimize ("unroll-loops")
#include <bits/stdc++.h>

using namespace std;

#define rep(i, a, b) for (int i = (a); i < (b); ++i)
#define per(i, a, b) for (int i = (b - 1); i >= (a); --i)
#define trav(a, x) for (auto &a : x)

#define all(x) x.begin(), x.end()
#define sz(x) x.size()
#define pb push_back
#define debug(x) cout << #x << " = " << x << endl

#define umap unordered_map
#define uset unordered_set

typedef pair<int, int> ii;
typedef pair<int, ii> iii;
typedef vector<int> vi;
typedef vector<ii> vii;
typedef vector<vi> vvi;

typedef long long ll;
typedef pair<ll, ll> pll;
typedef vector<ll> vll;
typedef vector<pll> vpll;

const int INF = 1'000'000'007;

int n, ans = INF, sub_size[200001], root;
set<int> nodes[200001];
vi graph[200001];

void dfs(int u, int p) {
    sub_size[u] = 1;
    trav(v, graph[u]) if (v != p) {
        dfs(v, u);
        sub_size[u] += sub_size[v];
        if (sz(nodes[u]) < sz(nodes[v])) nodes[u].swap(nodes[v]);
        trav(val, nodes[v]) nodes[u].insert(val);
        nodes[v].clear();
    }

    trav(v, graph[u]) if (v != p) nodes[u].insert(sub_size[v]);

    if (u != root && sub_size[u] != 1) {
        int above = n - sub_size[u];

        auto it = nodes[u].lower_bound(sub_size[u] / 2);
        if (it == nodes[u].end()) --it;

        {
            int p1 = *it, p2 = sub_size[u] - p1;
            int mx = max(above, max(p1, p2)), mn = min(above, min(p1, p2));

            ans = min(ans, mx - mn);
        }

        if (it != nodes[u].begin()) --it;

        {
            int p1 = *it, p2 = sub_size[u] - p1;
            int mx = max(above, max(p1, p2)), mn = min(above, min(p1, p2));

            ans = min(ans, mx - mn);
        }
    }
}

int main() {
    cin.tie(0)->sync_with_stdio(0);
    cin.exceptions(cin.failbit);

    cin >> n;
    rep(i, 1, n) {
        int u, v;
        cin >> u >> v;
        graph[--u].pb(--v);
        graph[v].pb(u);
    }

    rep(i, 0, 10) {
        root = rand()%n;
        dfs(root, root);
        nodes[root].clear();
    }

    cout << ans << endl;
    return 0;
}

• Subtask 1: 15 / 15
• Subtask 2: 35 / 35
• Subtask 3: 60 / 60