Submission #879791

#	Time	Username	Problem	Language	Result	Execution time	Memory
879791		TAhmed33	Papričice (COCI20_papricice)	C++98	110 / 110	128 ms	26140 KiB

papricice

#include <bits/stdc++.h>
using namespace std;
#pragma GCC optimize ("Ofast")
const int MAXN = 2e5 + 25;
const int bad = -1e7;
inline int comb (int a, int b, int c) {
    return abs(2 * a - c) < abs(2 * b - c) ? a : b;
}
vector <int> adj[MAXN];
int sze[MAXN], n, in[MAXN], out[MAXN], t;
int mn = 1e9; 
set <int> dfs (int pos, int par) {
    sze[pos] = 1;
    in[pos] = ++t;
    int mx = bad;
    set <int> cur;
    for (auto j : adj[pos]) {
        if (j == par) continue;
        auto x = dfs(j, pos);
        sze[pos] += sze[j];
        if (cur.size() < x.size()) cur.swap(x);
        for (auto i : x) cur.insert(i);
    }
    auto tt = cur.lower_bound(sze[pos] / 2);
    if (tt != cur.end()) mx = *tt;
    if (tt != cur.begin()) {
        tt--; mx = comb(mx, *tt, sze[pos]);
    }
    cur.insert(sze[pos]);
    if (sze[pos] != 1 && pos != 1) mn = min(mn, max({n - sze[pos], sze[pos] - mx, mx}) - min({n - sze[pos], sze[pos] - mx, mx}));
    out[pos] = t;
    return cur;
}
set <int> x;
void dfs2 (int pos, int par) {
    if (pos != 1 && !x.empty()) {
        auto t = x.lower_bound((n - sze[pos]) / 2);
        int ret = bad;
        if (t != x.end()) ret = *t;
        if (t != x.begin()) {
            t--;
            ret = comb(ret, *t, n - sze[pos]);
        }
        mn = min(mn, max({sze[pos], ret, n - sze[pos] - ret}) - min({sze[pos], ret, n - sze[pos] - ret}));
    }
    for (auto j : adj[pos]) if (j != par) dfs2(j, pos);
    x.insert(sze[pos]);
}
bool check (int x, int y) {
    return in[x] <= in[y] && in[y] <= out[x];
}
int main () {
    ios::sync_with_stdio(0);
    cin.tie(0);
    cin >> n;
    for (int i = 1; i < n; i++) {
        int a, b;
        cin >> a >> b;
        adj[a].push_back(b);
        adj[b].push_back(a);
    }
    dfs(1, -1);
    dfs2(1, -1);
    cout << mn << '\n';
}

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