結果
| 問題 |
No.1976 Cut then Connect
|
| コンテスト | |
| ユーザー |
 tokusakurai
|
| 提出日時 | 2022-06-10 22:34:30 |
| 言語 | C++17 (gcc 13.3.0 + boost 1.87.0) |
| 結果 |
WA
|
| 実行時間 | - |
| コード長 | 5,817 bytes |
| コンパイル時間 | 2,267 ms |
| コンパイル使用メモリ | 212,520 KB |
| 最終ジャッジ日時 | 2025-01-29 20:05:40 |
|
ジャッジサーバーID （参考情報） |
judge3 / judge2 |
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| ファイルパターン | 結果 |
|---|---|
| sample | AC * 2 |
| other | AC * 6 WA * 25 |
ソースコード
#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < n; i++)
#define rep2(i, x, n) for (int i = x; i <= n; i++)
#define rep3(i, x, n) for (int i = x; i >= n; i--)
#define each(e, v) for (auto &e : v)
#define pb push_back
#define eb emplace_back
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define sz(x) (int)x.size()
using ll = long long;
using pii = pair<int, int>;
using pil = pair<int, ll>;
using pli = pair<ll, int>;
using pll = pair<ll, ll>;
template <typename T>
bool chmax(T &x, const T &y) {
return (x < y) ? (x = y, true) : false;
}
template <typename T>
bool chmin(T &x, const T &y) {
return (x > y) ? (x = y, true) : false;
}
template <typename T>
int flg(T x, int i) {
return (x >> i) & 1;
}
template <typename T>
void print(const vector<T> &v, T x = 0) {
int n = v.size();
for (int i = 0; i < n; i++) cout << v[i] + x << (i == n - 1 ? '\n' : ' ');
if (v.empty()) cout << '\n';
}
template <typename T>
void printn(const vector<T> &v, T x = 0) {
int n = v.size();
for (int i = 0; i < n; i++) cout << v[i] + x << '\n';
}
template <typename T>
int lb(const vector<T> &v, T x) {
return lower_bound(begin(v), end(v), x) - begin(v);
}
template <typename T>
int ub(const vector<T> &v, T x) {
return upper_bound(begin(v), end(v), x) - begin(v);
}
template <typename T>
void rearrange(vector<T> &v) {
sort(begin(v), end(v));
v.erase(unique(begin(v), end(v)), end(v));
}
template <typename T>
vector<int> id_sort(const vector<T> &v, bool greater = false) {
int n = v.size();
vector<int> ret(n);
iota(begin(ret), end(ret), 0);
sort(begin(ret), end(ret), [&](int i, int j) { return greater ? v[i] > v[j] : v[i] < v[j]; });
return ret;
}
template <typename S, typename T>
pair<S, T> operator+(const pair<S, T> &p, const pair<S, T> &q) {
return make_pair(p.first + q.first, p.second + q.second);
}
template <typename S, typename T>
pair<S, T> operator-(const pair<S, T> &p, const pair<S, T> &q) {
return make_pair(p.first - q.first, p.second - q.second);
}
template <typename S, typename T>
istream &operator>>(istream &is, pair<S, T> &p) {
S a;
T b;
is >> a >> b;
p = make_pair(a, b);
return is;
}
template <typename S, typename T>
ostream &operator<<(ostream &os, const pair<S, T> &p) {
return os << p.first << ' ' << p.second;
}
struct io_setup {
io_setup() {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cout << fixed << setprecision(15);
}
} io_setup;
const int inf = (1 << 30) - 1;
const ll INF = (1LL << 60) - 1;
const int MOD = 1000000007;
// const int MOD = 998244353;
template <bool directed = false>
struct Graph {
struct edge {
int to, id;
edge(int to, int id) : to(to), id(id) {}
};
vector<vector<edge>> es;
const int n;
int m;
vector<int> d, si;
vector<bool> used;
vector<int> ma;
Graph(int n) : es(n), n(n), m(0), d(n), si(n), used(n, false), ma(n, 0) {}
void add_edge(int from, int to) {
es[from].emplace_back(to, m);
if (!directed) es[to].emplace_back(from, m);
m++;
}
void calc_depth(int now, int pre = -1) {
if (pre == -1) d[now] = 0;
for (auto &e : es[now]) {
if (e.to != pre) d[e.to] = d[now] + 1, calc_depth(e.to, now);
}
}
int calc_size(int now, int pre = -1) {
si[now] = 1;
for (auto &e : es[now]) {
if (e != pre) si[now] += calc_size(e.to, now);
}
return si[now];
}
int farthest_point(int s) {
calc_depth(s);
int max_d = -1, t = -1;
for (int i = 0; i < n; i++) {
if (d[i] > max_d) max_d = d[i], t = i;
}
return t;
}
pair<int, pair<int, int>> diameter() {
int a = farthest_point(0), b = farthest_point(a);
return make_pair(d[b], make_pair(a, b));
}
vector<int> ret_path;
bool detect_path(int now, int t, bool use_id = false, int pre = -1) {
if (now == t) {
if (!use_id) ret_path.push_back(now);
return true;
}
for (auto &e : es[now]) {
if (e.to == pre) continue;
if (detect_path(e.to, t, use_id, now)) {
ret_path.push_back(use_id ? e.id : now);
return true;
}
}
return false;
}
vector<int> find_path(int s, int t, bool use_id = false) {
ret_path.clear();
detect_path(s, t, use_id);
reverse(begin(ret_path), end(ret_path));
return ret_path;
}
void solve() {
rep(i, n - 1) {
int u, v;
cin >> u >> v;
u--, v--;
add_edge(u, v);
}
auto [s, t] = diameter().second;
vector<int> p = find_path(s, t);
each(e, p) used[e] = true;
each(e, p) ma[e] = dfs(e);
int K = sz(p);
vector<int> l(K - 1), r(K - 1);
rep(i, K - 1) {
if (i > 0) l[i] = l[i - 1];
chmax(l[i], i + ma[p[i]]);
}
rep3(i, K - 2, 0) {
if (i < K - 2) r[i] = r[i + 1];
chmax(r[i], K - 2 - i + ma[i + 1]);
}
int ans = inf;
rep(i, K - 1) {
int x = max(l[i], r[i]);
chmax(x, (l[i] + 1) / 2 + (r[i] + 1) / 2 + 1);
chmin(ans, x);
// cout << l[i] << ' ' << r[i] << ' ' << x << '\n';
}
cout << ans << '\n';
}
int dfs(int now, int pre = -1) {
int ret = 0;
each(e, es[now]) {
if (used[e.to] || e.to == pre) continue;
chmax(ret, dfs(e.to, now) + 1);
}
return ret;
}
};
int main() {
int N;
cin >> N;
Graph G(N);
G.solve();
}