結果

問題 No.1254 補強への架け橋
コンテスト
ユーザー hirono999
提出日時 2020-10-09 23:06:45
言語 C++17(gcc12)
(gcc 12.3.0 + boost 1.87.0)
結果
AC  
実行時間 325 ms / 2,000 ms
コード長 7,311 bytes
コンパイル時間 12,648 ms
コンパイル使用メモリ 308,488 KB
最終ジャッジ日時 2025-01-15 05:44:00
ジャッジサーバーID
（参考情報） 		judge4 / judge1
このコードへのチャレンジ
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ファイルパターン 結果
sample AC * 3
other AC * 123
権限があれば一括ダウンロードができます
コンパイルメッセージ
main.cpp: In function 'int main()':
main.cpp:236:18: warning: narrowing conversion of 'b' from 'll' {aka 'long long int'} to 'int' [-Wnarrowing]
  236 |         G[a].pb({b});
      |                  ^
main.cpp:237:18: warning: narrowing conversion of 'a' from 'll' {aka 'long long int'} to 'int' [-Wnarrowing]
  237 |         G[b].pb({a});
      |                  ^

ソースコード

diff #
raw source code 

#pragma GCC target("avx2")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#include <bits/stdc++.h>
constexpr long long INF = 1LL << 60;
double PI = acos(-1.0);
#define rep(i, n) for (ll i = 0; i < (n); ++i)
#define rep1(i, n) for (ll i = 1; i <= (n); ++i)
#define rrep(i, n) for (ll i = (n - 1); i >= 0; --i)
#define perm(c) sort(ALL(c));for(bool c##p=1;c##p;c##p=next_permutation(ALL(c)))
#define ALL(obj) (obj).begin(), (obj).end()
#define RALL(obj) (obj).rbegin(), (obj).rend()
#define pb push_back
#define to_s to_string
#define len(v) (ll)v.size()
#define UNIQUE(v) v.erase(unique(v.begin(), v.end()), v.end())
#define print(x) cout << (x) << '\n'
#define drop(x) cout << (x) << '\n', exit(0)
#define debug(x) cout << #x << ": " << (x) << '\n'
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<ll, ll> P;
typedef tuple<ll, ll, ll> tpl;
typedef vector<ll> vec;
typedef vector<vector<ll>> vec2;
typedef vector<vector<vector<ll>>> vec3;
template<class S, class T> inline bool chmax(S &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<class S, class T> inline bool chmin(S &a, const T &b) { if (b<a) { a=b; return 1; } return 0; }
inline ll msb(ll v) { return 1 << (31 - __builtin_clzll(v)); }
inline ll devc(ll x, ll y) { return (x + y - 1) / y; }
inline ll gcd(ll a, ll b) { return b ? gcd(b, a % b) : a; }
inline ll lcm(ll a, ll b) { return a * (b / gcd(a, b)); }
 
struct IoSetup {
    IoSetup() {
        cin.tie(nullptr);
        ios::sync_with_stdio(false);
        cout << fixed << setprecision(10);
        cerr << fixed << setprecision(10);
    }
} iosetup;
 
template< typename T1, typename T2 >
ostream &operator << (ostream &os, const pair< T1, T2 > &p) {
    os << p.first << " " << p.second;
    return os;
}
 
template< typename T1, typename T2 >
istream &operator >> (istream &is, pair< T1, T2 > &p) {
    is >> p.first >> p.second;
    return is;
}
 
template< typename T1, typename T2, typename T3 >
ostream &operator << (ostream &os, const tuple< T1, T2, T3 > &t) {
    os << get<0>(t) << " " << get<1>(t) << " " << get<2>(t);
    return os;
}
 
template< typename T1, typename T2, typename T3 >
istream &operator >> (istream &is, tuple< T1, T2, T3 > &t) {
    is >> get<0>(t) >> get<1>(t) >> get<2>(t);
    return is;
}
 
template< typename T >
ostream &operator << (ostream &os, const vector< T > &v){
    for (int i = 0; i < (int)v.size(); ++i) {
        os << v[i] << (i + 1 != v.size() ? " " : "");
    }
    return os;
}
 
template< typename T >
istream &operator >>  (istream &is, vector< T > &v){
    for(T &in : v) is >> in;
    return is;
}

template< typename T >
ostream &operator << (ostream &os, const set< T > &st){
    int ct = 0;
    for(auto& s : st) cout << s << (++ct != st.size() ? " " : "");
    return os;
}

template <typename T>
constexpr set<T> &operator|= (set<T> &st1, const set<T> &st2) { 
    for(auto& s : st2) st1.insert(s);
    return st1; 
}

template <typename T>
constexpr set<T> &operator-= (set<T> &st1, const set<T> &st2) {
    for(auto& s : st2) if(st1.count(s)) st1.erase(s);
    return st1;
}

template <typename T>
constexpr set<T> &operator&= (set<T> &st1, const set<T> &st2) {
    auto itr = st1.begin();
    while(itr != st1.end()){
        if(!st2.count(*itr)) itr = st1.erase(itr);
        else ++itr;
    }
    return st1;
}

template <typename T>
constexpr set<T> operator| (const set<T> &st1, const set<T> &st2) {
    set<T> res = st1;
    res |= st2;
    return res;
}

template <typename T>
constexpr set<T> operator- (const set<T> &st1, const set<T> &st2) {
    set<T> res = st1;
    res -= st2;
    return res;
}

template <typename T>
constexpr set<T> operator& (const set<T> &st1, const set<T> &st2) {
    set<T> res = st1;
    res &= st2;
    return res;
}

/*---------------------------------    Tools    ------------------------------------------*/
template< typename T >
vector<T> cumsum(const vector<T> &X){
    vector<T> res(X.size() + 1, 0);
    for(int i = 0; i < X.size(); ++i) res[i + 1] += res[i] + X[i];
    return res;
}
 
template< typename S, typename T, typename F>
pair<T, T> bisearch(S left, T right, F f) {
    while(abs(right - left) > 1){
        T mid = (right + left) / 2;
        if(f(mid)) right = mid;
        else left = mid;
    }
    return {left, right};
}
 
template< typename S, typename T, typename F>
double trisearch(S left, T right, F f, int maxLoop = 90){
    double low = left, high = right;
    while(maxLoop--){
        double mid_left = high / 3 + low * 2 / 3;
        double mid_right = high * 2 / 3 + low / 3;
        if(f(mid_left) >= f(mid_right)) low = mid_left;
        else high = mid_right;
    }
    return (low + high) * 0.5;
}

template< typename F >
ll ternarySearch(ll L, ll R, F f) { //[L, R)
    ll lo = L - 1, hi = R - 1;
    while (lo + 1 != hi) {
        ll mi = (lo + hi) / 2;
        if (f(mi) <= f(mi + 1)) hi = mi;
        else lo = mi;
    }
    return hi;
}

struct Edge {
    int to;
};
using Graph = vector<vector<Edge>>;
/* 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; // 条件2を満たすので関節点
                if (ord[id] < low[e.to]) bridges.emplace_back(min(id, e.to), max(id, e.to));  
            } 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; // 条件1を満たすので関節点
        if (is_aps) aps.push_back(id);
        return k;
    }
};

// #include <atcoder/all>
// using namespace atcoder;
constexpr long long MOD = 1000000007;
/*------------------------------- Main Code Here -----------------------------------------*/
 
int main()
{
    ll N;
    cin >> N;
    Graph G(N);
    map<P, ll> bridge;
    rep(i, N){
        ll a, b;
        cin >> a >> b;
        --a, --b;
        G[a].pb({b});
        G[b].pb({a});
        bridge[{a, b}] = i;
        bridge[{b, a}] = i;
    }
    LowLink LK(G);
    set<ll> ans;
    rep1(i, N) ans.insert(i);
    for(auto p : LK.bridges){
        ans.erase(bridge[p] + 1);
    }
    print(len(ans));
    print(ans);

    return 0;
}
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