結果

問題 No.1553 Lovely City
ユーザー tokusakurai
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
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 * 2
other AC * 26
権限があれば一括ダウンロードができます

ソースコード

diff #
プレゼンテーションモードにする

#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';
}
}
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