Submission #879767

#	Time	Username	Problem	Language	Result	Execution time	Memory
879767		TAhmed33	Papričice (COCI20_papricice)	C++98	15 / 110	12 ms	36188 KiB

papricice

#include <bits/stdc++.h>
using namespace std;
const int MAXN = 2e5 + 25;
#define mid ((l + r) >> 1)
#define tl (node + 1)
#define tr (node + 2 * (mid - l + 1))
const int bad = -1e9;
int comb (int a, int b, int c) {
    return abs(2 * a - c) < abs(2 * b - c) ? a : b;
}
struct SegmentTree {
    set <int> tree[2 * MAXN];
    int arr[MAXN];
    void build (int l, int r, int node) {
        for (int i = l; i <= r; i++) tree[node].insert(arr[i]);
        if (l == r) return;
        build(l, mid, tl); build(mid + 1, r, tr);
    }
    int get (int l, int r, int a, int b, int c, int node) {
        if (a > b || l > r) return bad;
        if (l > b || r < a) return bad;
        if (l >= a && r <= b) {
            int ret = bad;
            auto t = tree[node].lower_bound(c);
            if (t != tree[node].end()) ret = comb(ret, *t, c);
            if (t != tree[node].begin()) {
                t--;
                ret = comb(ret, *t, c);
            }
            return ret;
        }
        return comb(get(l, mid, a, b, c, tl), get(mid + 1, r, a, b, c, tr), c);
    }
} cur;
vector <int> adj[MAXN];
int sze[MAXN], n, in[MAXN], out[MAXN], t;
set <int> dd[MAXN];
typedef long long ll;
int mn = 1e9; 
void dfs (int pos, int par) {
	sze[pos] = 1;
	in[pos] = ++t;
    int mx = bad;
	for (auto j : adj[pos]) {
		if (j == par) continue;
		dfs(j, pos);
		sze[pos] += sze[j];
        if (dd[pos].size() < dd[j].size()) swap(dd[pos], dd[j]);
        for (auto i : dd[j]) dd[pos].insert(i);
        dd[j].clear();
	}
    dd[pos].insert(sze[pos]);
    for (auto i : dd[pos]) {
        if (abs(2 * i - sze[pos]) < abs(2 * mx - sze[pos])) {
            mx = i;
        }
    }
    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;
}
bool check (int x, int y) {
	return in[y] < in[x] && in[x] <= out[y];
}
int main () {
	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);
    for (int i = 2; i <= n; i++) {
        cur.arr[in[i]] = sze[i];
    }
    cur.build(2, n, 1);
	for (int i = 2; i <= n; i++) {
        int x = comb(cur.get(2, n, 2, in[i] - 1, n - sze[i], 1), cur.get(2, n, out[i] + 1, n, n - sze[i], 1), n - sze[i]);
        mn = min(mn, max({sze[i], x, n - x - sze[i]}) - min({sze[i], x, n - sze[i] - x}));
	}
	cout << mn << '\n';
}

• Subtask 1: 15 / 15
• Subtask 2: 0 / 35
• Subtask 3: 0 / 60