結果
| 問題 |
No.1254 補強への架け橋
|
| コンテスト | |
| ユーザー |
 iiljj
|
| 提出日時 | 2020-10-09 22:49:51 |
| 言語 | C++17 (gcc 13.3.0 + boost 1.87.0) |
| 結果 |
AC
|
| 実行時間 | 518 ms / 2,000 ms |
| コード長 | 8,900 bytes |
| コンパイル時間 | 3,551 ms |
| コンパイル使用メモリ | 224,836 KB |
| 最終ジャッジ日時 | 2025-01-15 05:28:12 |
|
ジャッジサーバーID （参考情報） |
judge2 / judge3 |
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| ファイルパターン | 結果 |
|---|---|
| sample | AC * 3 |
| other | AC * 123 |
ソースコード
/* #region Head */
// #define _GLIBCXX_DEBUG
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ull = unsigned long long;
using ld = long double;
using pll = pair<ll, ll>;
template <class T> using vc = vector<T>;
template <class T> using vvc = vc<vc<T>>;
using vll = vc<ll>;
using vvll = vvc<ll>;
using vld = vc<ld>;
using vvld = vvc<ld>;
using vs = vc<string>;
using vvs = vvc<string>;
template <class T, class U> using um = unordered_map<T, U>;
template <class T> using pq = priority_queue<T>;
template <class T> using pqa = priority_queue<T, vc<T>, greater<T>>;
template <class T> using us = unordered_set<T>;
#define REP(i, m, n) for (ll i = (m), i##_len = (ll)(n); i < i##_len; ++(i))
#define REPM(i, m, n) for (ll i = (m), i##_max = (ll)(n); i <= i##_max; ++(i))
#define REPR(i, m, n) for (ll i = (m), i##_min = (ll)(n); i >= i##_min; --(i))
#define REPD(i, m, n, d) for (ll i = (m), i##_len = (ll)(n); i < i##_len; i += (d))
#define REPMD(i, m, n, d) for (ll i = (m), i##_max = (ll)(n); i <= i##_max; i += (d))
#define REPI(itr, ds) for (auto itr = ds.begin(); itr != ds.end(); itr++)
#define ALL(x) begin(x), end(x)
#define SIZE(x) ((ll)(x).size())
#define PERM(c) \
sort(ALL(c)); \
for (bool c##p = 1; c##p; c##p = next_permutation(ALL(c)))
#define UNIQ(v) v.erase(unique(ALL(v)), v.end());
#define endl '\n'
#define sqrt sqrtl
#define floor floorl
#define log2 log2l
constexpr ll INF = 1'010'000'000'000'000'017LL;
constexpr int IINF = 1'000'000'007LL;
constexpr ll MOD = 1'000'000'007LL; // 1e9 + 7
// constexpr ll MOD = 998244353;
constexpr ld EPS = 1e-12;
constexpr ld PI = 3.14159265358979323846;
template <typename T> istream &operator>>(istream &is, vc<T> &vec) { // vector 入力
for (T &x : vec) is >> x;
return is;
}
template <typename T> ostream &operator<<(ostream &os, vc<T> &vec) { // vector 出力 (for dump)
os << "{";
REP(i, 0, SIZE(vec)) os << vec[i] << (i == i_len - 1 ? "" : ", ");
os << "}";
return os;
}
template <typename T> ostream &operator>>(ostream &os, vc<T> &vec) { // vector 出力 (inline)
REP(i, 0, SIZE(vec)) os << vec[i] << (i == i_len - 1 ? "\n" : " ");
return os;
}
template <typename T, typename U> istream &operator>>(istream &is, pair<T, U> &pair_var) { // pair 入力
is >> pair_var.first >> pair_var.second;
return is;
}
template <typename T, typename U> ostream &operator<<(ostream &os, pair<T, U> &pair_var) { // pair 出力
os << "(" << pair_var.first << ", " << pair_var.second << ")";
return os;
}
// map, um, set, us 出力
template <class T> ostream &out_iter(ostream &os, T &map_var) {
os << "{";
REPI(itr, map_var) {
os << *itr;
auto itrcp = itr;
if (++itrcp != map_var.end()) os << ", ";
}
return os << "}";
}
template <typename T, typename U> ostream &operator<<(ostream &os, map<T, U> &map_var) { return out_iter(os, map_var); }
template <typename T, typename U> ostream &operator<<(ostream &os, um<T, U> &map_var) {
os << "{";
REPI(itr, map_var) {
auto [key, value] = *itr;
os << "(" << key << ", " << value << ")";
auto itrcp = itr;
if (++itrcp != map_var.end()) os << ", ";
}
os << "}";
return os;
}
template <typename T> ostream &operator<<(ostream &os, set<T> &set_var) { return out_iter(os, set_var); }
template <typename T> ostream &operator<<(ostream &os, us<T> &set_var) { return out_iter(os, set_var); }
template <typename T> ostream &operator<<(ostream &os, pq<T> &pq_var) {
pq<T> pq_cp(pq_var);
os << "{";
if (!pq_cp.empty()) {
os << pq_cp.top(), pq_cp.pop();
while (!pq_cp.empty()) os << ", " << pq_cp.top(), pq_cp.pop();
}
return os << "}";
}
// dump
#define DUMPOUT cerr
void dump_func() { DUMPOUT << endl; }
template <class Head, class... Tail> void dump_func(Head &&head, Tail &&... tail) {
DUMPOUT << head;
if (sizeof...(Tail) > 0) DUMPOUT << ", ";
dump_func(move(tail)...);
}
// chmax (更新「される」かもしれない値が前)
template <typename T, typename U, typename Comp = less<>> bool chmax(T &xmax, const U &x, Comp comp = {}) {
if (comp(xmax, x)) {
xmax = x;
return true;
}
return false;
}
// chmin (更新「される」かもしれない値が前)
template <typename T, typename U, typename Comp = less<>> bool chmin(T &xmin, const U &x, Comp comp = {}) {
if (comp(x, xmin)) {
xmin = x;
return true;
}
return false;
}
// ローカル用
#define DEBUG_
#ifdef DEBUG_
#define DEB
#define dump(...) \
DUMPOUT << " " << string(#__VA_ARGS__) << ": " \
<< "[" << to_string(__LINE__) << ":" << __FUNCTION__ << "]" << endl \
<< " ", \
dump_func(__VA_ARGS__)
#else
#define DEB if (false)
#define dump(...)
#endif
#define VAR(type, ...) \
type __VA_ARGS__; \
cin >> __VA_ARGS__;
template <typename T> istream &operator,(istream &is, T &rhs) { return is >> rhs; }
template <typename T> ostream &operator,(ostream &os, const T &rhs) { return os << ' ' << rhs; }
struct AtCoderInitialize {
static constexpr int IOS_PREC = 15;
static constexpr bool AUTOFLUSH = false;
AtCoderInitialize() {
ios_base::sync_with_stdio(false), cin.tie(nullptr), cout.tie(nullptr);
cout << fixed << setprecision(IOS_PREC);
if (AUTOFLUSH) cout << unitbuf;
}
} ATCODER_INITIALIZE;
void Yn(bool p) { cout << (p ? "Yes" : "No") << endl; }
void YN(bool p) { cout << (p ? "YES" : "NO") << endl; }
/* #endregion */
// #include <atcoder/all>
// using namespace atcoder;
struct Edge {
int to;
};
using Graph = vector<vector<Edge>>;
using P = pair<long, long>;
/* Lowlink: グラフの関節点・橋を列挙する構造体
作成: O(E+V)
関節点の集合: vector<int> aps
橋の集合: vector<P> bridges
*/
struct LowLink {
const Graph &G;
vector<int> used, ord, low;
vector<int> aps; // articulation points
vector<P> bridges;
LowLink(const Graph &G_) : G(G_) {
used.assign(G.size(), 0);
ord.assign(G.size(), 0);
low.assign(G.size(), 0);
int k = 0;
for (int i = 0; i < (int)G.size(); i++) {
if (!used[i]) k = dfs(i, k, -1);
}
sort(aps.begin(), aps.end()); // 必要ならソートする
sort(bridges.begin(), bridges.end()); // 必要ならソートする
}
int dfs(int id, int k, int par) { // id:探索中の頂点, k:dfsで何番目に探索するか, par:idの親
used[id] = true;
ord[id] = k++;
low[id] = ord[id];
bool is_aps = false;
int count = 0; // 子の数
for (auto &e : G[id]) {
if (!used[e.to]) {
count++;
k = dfs(e.to, k, id);
low[id] = min(low[id], low[e.to]);
if (par != -1 && ord[id] <= low[e.to]) is_aps = true;
if (ord[id] < low[e.to]) bridges.emplace_back(min(id, e.to), max(id, e.to)); // 条件を満たすので橋
} else if (e.to != par) { // eが後退辺の時
low[id] = min(low[id], ord[e.to]);
}
}
if (par == -1 && count >= 2) is_aps = true;
if (is_aps) aps.push_back(id);
return k;
}
};
// Problem
void solve() {
// 取り去っても木が維持されるような辺を除去したい，そのような辺を探す
// -> ループからは1個とっても大丈夫
VAR(ll, n);
map<P, ll> edgenum;
set<ll> edgenumset;
Graph g(n);
REP(i, 0, n) {
VAR(int, a, b);
--a, --b;
P key0 = {a, b};
P key1 = {b, a};
edgenum[key0] = i + 1;
edgenum[key1] = i + 1;
g[a].push_back({b});
g[b].push_back({a});
edgenumset.insert(i + 1);
}
LowLink lnk(g);
for (auto &bridge : lnk.bridges) {
ll num = edgenum[bridge];
edgenumset.erase(num);
}
vll out;
for (ll num : edgenumset) out.push_back(num);
cout << SIZE(out) << endl;
cout >> out;
}
// entry point
int main() {
solve();
return 0;
}