結果
問題 | No.1553 Lovely City |
ユーザー |
|
提出日時 | 2021-06-19 10:39:30 |
言語 | C++17 (gcc 13.3.0 + boost 1.87.0) |
結果 |
AC
|
実行時間 | 294 ms / 2,000 ms |
コード長 | 4,452 bytes |
コンパイル時間 | 2,725 ms |
コンパイル使用メモリ | 217,916 KB |
最終ジャッジ日時 | 2025-01-22 09:57:06 |
ジャッジサーバーID (参考情報) |
judge5 / judge2 |
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ファイルパターン | 結果 |
---|---|
sample | AC * 2 |
other | AC * 26 |
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>;const int MOD = 1000000007;//const int MOD = 998244353;const int inf = (1<<30)-1;const ll INF = (1LL<<60)-1;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;};struct io_setup{io_setup(){ios_base::sync_with_stdio(false);cin.tie(NULL);cout << fixed << setprecision(15);}} io_setup;struct Union_Find_Tree{vector<int> data;const int n;Union_Find_Tree(int n) : data(n, -1), n(n) {}int root(int x){if(data[x] < 0) return x;return data[x] = root(data[x]);}int operator [] (int i) {return root(i);}bool unite(int x, int y){x = root(x), y = root(y);if(x == y) return false;if(data[x] > data[y]) swap(x, y);data[x] += data[y], data[y] = x;return true;}int size(int x) {return -data[root(x)];}bool same(int x, int y) {return root(x) == root(y);}void clear() {fill(begin(data), end(data), -1);}};template<bool directed = true>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;Graph(int n) : es(n), n(n), m(0) {}void add_edge(int from, int to){es[from].emplace_back(to, m);if(!directed) es[to].emplace_back(from, m);m++;}};template<bool directed = true>struct Strongly_Connected_Components{struct edge{int to, id;edge(int to, int id) : to(to), id(id) {}};vector<vector<edge>> es, rs;vector<int> vs, comp;vector<bool> used;const int n;int m;Strongly_Connected_Components(int n) : es(n), rs(n), vs(n), comp(n), used(n), n(n), m(0) {}void add_edge(int from, int to){es[from].emplace_back(to, m), rs[to].emplace_back(from, m);if(!directed) es[to].emplace_back(from, m), rs[from].emplace_back(to, m);m++;}void _dfs(int now){used[now] = true;for(auto &e: es[now]){if(!used[e.to]) _dfs(e.to);}vs.push_back(now);}void _rdfs(int now, int cnt){used[now] = true, comp[now] = cnt;for(auto &e: rs[now]){if(!used[e.to]) _rdfs(e.to, cnt);}}Graph<true> decompose(){fill(begin(used), end(used), false);for(int i = 0; i < n; i++){if(!used[i]) _dfs(i);}fill(begin(used), end(used), false), reverse(begin(vs), end(vs));int cnt = 0;for(auto &e: vs){if(!used[e]) _rdfs(e, cnt++);}Graph<true> G(cnt);for(int i = 0; i < n; i++){for(auto &e: es[i]){int u = comp[i], v = comp[e.to];if(u != v) G.add_edge(u, v);}}return G;}int operator [] (int k) const {return comp[k];}};int main(){int N, M; cin >> N >> M;Union_Find_Tree uf(N);Strongly_Connected_Components G(N);rep(i, M){int u, v; cin >> u >> v; u--, v--;uf.unite(u, v);G.add_edge(u, v);}G.decompose();vector<vector<int>> ids(N);vector<pii> ans;rep(i, N){ids[uf[i]].eb(i);}rep(i, N){sort(all(ids[i]), [&](int a, int b){return G.comp[a] < G.comp[b];});bool flag = false;rep(j, sz(ids[i])-1){if(G.comp[ids[i][j]] == G.comp[ids[i][j+1]]){flag = true;}}rep(j, sz(ids[i])-1){ans.eb(ids[i][j], ids[i][j+1]);}if(flag){ans.eb(ids[i].back(), ids[i].front());}}cout << sz(ans) << '\n';each(e, ans){cout << e.first+1 << ' ' << e.second+1 << '\n';}}