#include <bits/stdc++.h>
using namespace std;
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
template<typename T> using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
template<typename T, typename U> using ordered_map = tree<T, U, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
typedef long long ll;
typedef long double ld;
typedef double db;
typedef string str;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef vector<pii> vpii;
typedef vector<pll> vpll;
typedef vector<str> vstr;
#define FOR(i,j,k,in) for(int i=(j); i < (k);i+=in)
#define FORD(i,j,k,in) for(int i=(j); i >=(k);i-=in)
#define REP(i,b) FOR(i,0,b,1)
#define REPD(i,b) FORD(i,b,0,1)
#define pb push_back
#define mp make_pair
#define ff first
#define ss second
#define all(x) begin(x), end(x)
#define rsz resize
const double EPS = 1e-9;
const int MOD = 1e9+7; // 998244353;
const ll INFF = 1e18;
const int INF = 1e9;
const ld PI = acos((ld)-1);
const vi dy = {1, 0, -1, 0, -1, 1, 1, -1};
const vi dx = {0, 1, 0, -1, -1, 1, -1, 1};
#ifdef DEBUG
#define DBG if(1)
#else
#define DBG if(0)
#endif
#define dbg(x) cout << "(" << #x << " : " << x << ")" << endl;
// ostreams
template <class T, class U>
ostream& operator<<(ostream& out, const pair<T, U> &par) {out << "[" << par.first << ";" << par.second << "]"; return out;}
template <class T>
ostream& operator<<(ostream& out, const set<T> &cont) { out << "{"; for( const auto &x:cont) out << x << ", "; out << "}"; return out; }
template <class T, class U>
ostream& operator<<(ostream& out, const map<T, U> &cont) {out << "{"; for( const auto &x:cont) out << x << ", "; out << "}"; return out; }
template<class T>
ostream& operator<<(ostream& out, const vector<T> &v){ out << "["; REP(i, v.size()) out << v[i] << ", "; out << "]"; return out;}
// istreams
template<class T>
istream& operator>>(istream& in, vector<T> &v){ for(auto &x : v) in >> x; return in; }
template<class T, class U>
istream& operator>>(istream& in, pair<T, U> &p){ in >> p.ff >> p.ss; return in; }
//searches
template<typename T, typename U>
T bsl(T lo, T hi, U f){ hi++; T mid; while(lo < hi){ mid = (lo + hi)/2; f(mid) ? hi = mid : lo = mid+1; } return lo; }
template<typename U>
double bsld(double lo, double hi, U f, double p = 1e-9){ int r = 3 + (int)log2((hi - lo)/p); double mid; while(r--){ mid = (lo + hi)/2; f(mid) ? hi = mid : lo = mid; } return (lo + hi)/2; }
template<typename T, typename U>
T bsh(T lo, T hi, U f){ lo--; T mid; while(lo < hi){ mid = (lo + hi + 1)/2; f(mid) ? lo = mid : hi = mid-1; } return lo; }
template<typename U>
double bshd(double lo, double hi, U f, double p = 1e-9){ int r = 3+(int)log2((hi - lo)/p); double mid; while(r--){ mid = (lo + hi)/2; f(mid) ? lo = mid : hi = mid; } return (lo + hi)/2; }
// some more utility functions
template<typename T>
pair<T, int> get_min(vector<T> &v){ typename vector<T> :: iterator it = min_element(v.begin(), v.end()); return mp(*it, it - v.begin());}
template<typename T>
pair<T, int> get_max(vector<T> &v){ typename vector<T> :: iterator it = max_element(v.begin(), v.end()); return mp(*it, it - v.begin());}
template<typename T> bool ckmin(T& a, const T& b){return b < a ? a = b , true : false;}
template<typename T> bool ckmax(T& a, const T& b){return b > a ? a = b, true : false;}
//practically constant time - dsu with path compression
// if(e[x] < 0) e[x] is root and size is -e[x] else e[x] is parent of x;
// kactl icpc notebook
struct dsu{
vector<int> e;
dsu(){};
dsu(int n){
e.resize(n, -1);
}
int find(int x){ return (e[x] < 0 ? x : e[x] = find(e[x])); }
int size(int x){ return -e[find(x)]; }
int sameSet(int a, int b){ return find(a) == find(b); }
bool join(int a, int b){
a = find(a); b = find(b);
if(a == b) return false;
if(e[a] > e[b]) swap(a, b);
e[a] += e[b]; e[b] = a;
return true;
}
};
const int mx = (int)1e5 + 5;
int in[mx]; int low[mx];
vector<int> adj[mx];
int t = 0;
void dfs(int v, int p){
++t; in[v] = t; low[v] = INF;
sort(all(adj[v]));
REP(i, adj[v].size()){
if(adj[v][i] == p) continue;
if(in[adj[v][i]] == -1){
dfs(adj[v][i], v);
bool can_bridge = true;
if(i && adj[v][i-1] == adj[v][i]) can_bridge = false;
if(i < adj[v].size()-1 && adj[v][i+1] == adj[v][i]) can_bridge = false;
if(low[adj[v][i]] > in[v] && can_bridge){
cout << v+1 << " " << adj[v][i]+1 << endl;
}
low[v] = min(low[v], low[adj[v][i]]);
}
else if(in[v] > in[adj[v][i]]) low[v] = min(low[v], in[adj[v][i]]);
}
}
int main(){
ios_base::sync_with_stdio(false);
cin.tie(NULL); cout.tie(NULL);
int n, m;
cin >> n >> m;
dsu comp(n); // connected components;
dsu bcc(n); // biconnected components;
REP(i, m){
int a, b; cin >> a >> b;
--a; --b;
bool discard = true;
if(!comp.sameSet(a,b)){
comp.join(a,b);
discard = false;
}
else if(!bcc.sameSet(a, b)){
bcc.join(a,b);
discard = false;
}
if(!discard){
adj[a].pb(b);
adj[b].pb(a);
}
}
REP(i, n) in[i] = -1;
REP(i, n)
if(in[i] == -1) dfs(i, -1);
return 0;
}
Compilation message
pipes.cpp: In function 'void dfs(int, int)':
pipes.cpp:26:40: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
26 | #define FOR(i,j,k,in) for(int i=(j); i < (k);i+=in)
| ^
pipes.cpp:28:18: note: in expansion of macro 'FOR'
28 | #define REP(i,b) FOR(i,0,b,1)
| ^~~
pipes.cpp:111:5: note: in expansion of macro 'REP'
111 | REP(i, adj[v].size()){
| ^~~
pipes.cpp:117:18: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
117 | if(i < adj[v].size()-1 && adj[v][i+1] == adj[v][i]) can_bridge = false;
| ~~^~~~~~~~~~~~~~~~~
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
2 ms |
2688 KB |
Output is correct |
| 2 |
Correct |
2 ms |
2688 KB |
Output is correct |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
7 ms |
3200 KB |
Output is correct |
| 2 |
Correct |
6 ms |
2944 KB |
Output is correct |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
119 ms |
3064 KB |
Output is correct |
| 2 |
Correct |
118 ms |
2936 KB |
Output is correct |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
210 ms |
3832 KB |
Output is correct |
| 2 |
Correct |
224 ms |
3320 KB |
Output is correct |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
309 ms |
5412 KB |
Output is correct |
| 2 |
Correct |
291 ms |
5092 KB |
Output is correct |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
440 ms |
10728 KB |
Output is correct |
| 2 |
Correct |
401 ms |
7376 KB |
Output is correct |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
674 ms |
12008 KB |
Output is correct |
| 2 |
Correct |
710 ms |
12536 KB |
Output is correct |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
965 ms |
14168 KB |
Output is correct |
| 2 |
Correct |
904 ms |
11156 KB |
Output is correct |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
1081 ms |
14204 KB |
Output is correct |
| 2 |
Correct |
1080 ms |
15152 KB |
Output is correct |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
1320 ms |
13560 KB |
Output is correct |
| 2 |
Correct |
1341 ms |
10760 KB |
Output is correct |
