Submission #763499

#	Time	Username	Problem	Language	Result	Execution time	Memory
763499		fanwen	Papričice (COCI20_papricice)	C++17	110 / 110	198 ms	23360 KiB

papricice

/**
 *      author : pham van sam
 *      created : 22 June 2023 (Thursday)
 **/

#include <bits/stdc++.h>

using namespace std;
using namespace chrono;

#define MASK(x) (1LL << (x))
#define BIT(x, i) (((x) >> (i)) & 1)
#define ALL(x) (x).begin(), (x).end()
#define REP(i, n) for (int i = 0, _n = n; i < _n; ++i)
#define FOR(i, a, b) for (int i = (a), _b = (b); i <= _b; ++i)
#define FORD(i, a, b) for (int i = (a), _b = (b); i >= _b; --i)
#define FORE(it, s) for (__typeof(s.begin()) it = (s).begin(); it != (s).end(); ++it)

template <typename U, typename V> bool maximize(U &A, const V &B) { return (A < B) ? (A = B, true) : false; }
template <typename U, typename V> bool minimize(U &A, const V &B) { return (A > B) ? (A = B, true) : false; }

const int MAXN = 2e5 + 5;

int N, num_child[MAXN], ans;
vector <int> adj[MAXN];

void dfs(int u, int p) {
	num_child[u] = 1;
	for (auto v : adj[u]) if(v != p) {
		dfs(v, u);
		num_child[u] += num_child[v];
	}
}

int get(int a, int b, int c) {
	if(a > b) swap(a, b);
	return max(b, c) - min(a, c);
}
set <int> same, diff;

vector <int> optimize(set <int> &s, int res) {
	auto it = s.upper_bound(res);
	vector <int> ans;
	if(it != s.end()) ans.push_back(*it);
	if(it != s.begin()) it--, ans.push_back(*it);
	return ans;
}

void calc(int u, int p) {
	for (auto x : optimize(same, (N + num_child[u]) / 2)) minimize(ans, get(num_child[u], x - num_child[u], N - x));
	for (auto x : optimize(diff, (N - num_child[u]) / 2)) minimize(ans, get(num_child[u], x, N - num_child[u] - x));
	same.insert(num_child[u]);
	for (auto v : adj[u]) if(v != p) calc(v, u);
	same.erase(num_child[u]);
	
	diff.insert(num_child[u]);
}

void process(void) {
	cin >> N;
	FOR(i, 2, N) {
		int u, v; cin >> u >> v;
		adj[u].push_back(v);
		adj[v].push_back(u);
	}
	dfs(1, 0);
	ans = N;
	calc(1, 0);
	cout << ans;
}

signed main() {

    #define TASK "TASK"
    if(fopen(TASK".inp", "r")) {
        freopen(TASK".inp", "r", stdin);
        freopen(TASK".out", "w", stdout);
    }

    ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);

    auto start_time = steady_clock::now();
    int test = 1;
    // cin >> test;
    for (int i = 1; i <= test; ++i) {
        process();
        // cout << '\n';
    }

    auto end_time = steady_clock::now();

    cerr << "\nExecution time : " << duration_cast<milliseconds> (end_time - start_time).count() << "[ms]" << endl;

    return (0 ^ 0);
}

Compilation message (stderr)

papricice.cpp: In function 'int main()':
papricice.cpp:76:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   76 |         freopen(TASK".inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
papricice.cpp:77:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   77 |         freopen(TASK".out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

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