#include <bits/stdc++.h>
// #define int int64_t //be careful about this
using namespace std;
#define vt vector
#define ar array
#define pr pair
#define f first
#define s second
#define pb push_back
#define eb emplace_back
#define fr(i,a,b) for(int i = (a); i < (b); ++i)
#define rf(i,a,b) for(int i = (b)-1; i >= (a); --i)
#define all(x) x.begin(),x.end()
#define mem(a,b) memset(a,b,sizeof(a))
namespace IN{
template<class T> void re(vector<T> &A);
template<class S,class T> void re(pair<S,T> &A);
template<class T,size_t N> void re(array<T,N> &A);
template<class T> void re(T& x){
cin >> x;}
template<class H, class... T> void re(H& h, T&... t){
re(h); re(t...);}
template<class T> void re(vector<T> &A){
for(auto& x : A) re(x);}
template<class S,class T> void re(pair<S,T> &A){
re(A.first); re(A.second);}
template<class T,size_t N> void re(array<T,N> &A){
for(int i = 0; i < N; ++i) re(A[i]);}
}
namespace OUT{
template<class T>
void __p(const T& a){ cout<<a; }
template<class T, class F>
void __p(const pair<T, F>& a){ cout<<"{"; __p(a.first); cout<<","; __p(a.second); cout<<"}\n"; }
template<class T, size_t N>
void __p(const array<T,N>& a){ cout<<"{"; for(int i=0;i<N;++i)__p(a[i]),cout<<",}\n"[i+1==N]; }
template<class T>
void __p(const vector<T>& a){
cout<<"{";for(auto it=a.begin();it<a.end();it++)__p(*it),cout<<",}\n"[it+1==a.end()]; }
template<class T, class ...Arg>
void __p(T a1, Arg ...a){__p(a1); __p(a...); }
template<class Arg1>
void __f(const char *s, Arg1 &&arg1){ cout<<s<<" : "; __p(arg1); cout<<endl; }
template<class Arg1, class ... Args>
void __f(const char *ss, Arg1 &&arg1, Args &&... args){
int b=0,i=0; do{ if(ss[i]=='(') b++; if(ss[i]==')') b--; i++;}while(!(ss[i]==','&&b==0));
const char *comma=ss+i; cout.write(ss,comma-ss)<<" : ";__p(arg1);cout<<" | ";__f(comma+1,args...);}
#define trace(...) cout<<"Line:"<<__LINE__<<" ", __f(#__VA_ARGS__, __VA_ARGS__)
}
namespace FUNC{
void IO(string s = ""){
ios_base::sync_with_stdio(NULL);
cin.tie(nullptr);
cout.precision(20);
cout << fixed;
if(!s.empty()){
freopen((s+".in").c_str(),"r",stdin);
freopen((s+".out").c_str(),"w",stdout);
}
}
const auto start_time = chrono::high_resolution_clock::now();
void output_run_time(){
// will work for ac,cc&&cf.
#ifndef ONLINE_JUDGE
auto end_time = chrono::high_resolution_clock::now();
chrono::duration<double> diff = end_time-start_time;
cout << "\n\n\nTime Taken : " << diff.count();
#endif
}
template<class T> bool ckmin(T& a, const T& b){
return b < a ? a = b, true : false; }
template<class T> bool ckmax(T& a, const T& b){
return a < b ? a = b, true : false; }
mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
int my_rand(int L, int R){
return uniform_int_distribution<int>(L,R)(rng); }
template<class T> int sz(const T& x){
return int(x.size()); }
template<class T> int lb(const vector<T>& vec,const T& val){
return int(lower_bound(vec.begin(), vec.end(),val) - vec.begin()); }
template<class T> int ub(const vector<T>& vec,const T& val){
return int(upper_bound(vec.begin(), vec.end(),val) - vec.begin()); }
constexpr int dx[4] = {1,0,-1,0};
constexpr int dy[4] = {0,1,0,-1};
constexpr char dr[4] = {'D','R','U','L'};
constexpr long long INFLL1 = 1e16, INFLL2 = 9e18;
constexpr int INF = 2e9;
template<class T>
vector<T> V(int n,T val){
return vector<T> (n,val);
}
template<class T>
vector<vector<T>> V(int n,int m,T val){
return vector<vector<T>> (n,vector<T> (m,val));
}
template<class T>
vector<vector<vector<T>>> V(int n,int m,int k,T val){
return vector<vector<vector<T>>> (n,vector<vector<T>> (m,vector<T> (k,val)));
}
}
using namespace IN;
using namespace OUT;
using namespace FUNC;
struct edge{
int to;
};
signed main(){
IO();
int n,m;
re(n,m);
vt<vt<edge>> g(n);
fr(e,0,m){
int u,v; re(u,v); --u,--v;
g[u].pb({v}); g[v].pb({u});
}
vector<int> depth(n,-1), low(n);
vt<pr<int,int>> ans;
auto dfs = [&](auto self,int node,int parent) -> void {
low[node] = depth[node];
bool f = false;
for(auto [child] : g[node])
if(child != parent || f){
if(depth[child] < 0){
depth[child] = depth[node] + 1;
self(self,child,node);
low[node] = min(low[node],low[child]);
}else if(depth[child] < depth[node]){
low[node] = min(low[node],depth[child]);
}
}else{
f = true;
}
if(low[node] == depth[node] && parent >= 0){
ans.pb({node,parent});
}
return;
};
fr(i,0,n) if(depth[i] < 0) depth[i] = 0, dfs(dfs,i,-1);
cout << sz(ans) << "\n";
for(auto [u,v] : ans)
cout << u+1 << " " << v+1 << "\n";
// output_run_time();
return 0;
}
Compilation message
pipes.cpp: In function 'void FUNC::IO(std::string)':
pipes.cpp:68:14: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
68 | freopen((s+".in").c_str(),"r",stdin);
| ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
pipes.cpp:69:14: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
69 | freopen((s+".out").c_str(),"w",stdout);
| ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
1 ms |
212 KB |
Unexpected end of file - int32 expected |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
4 ms |
1108 KB |
Unexpected end of file - int32 expected |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
107 ms |
14244 KB |
Unexpected end of file - int32 expected |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Runtime error |
215 ms |
22156 KB |
Memory limit exceeded |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Runtime error |
481 ms |
40796 KB |
Memory limit exceeded |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Runtime error |
730 ms |
54420 KB |
Memory limit exceeded |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Runtime error |
1048 ms |
65536 KB |
Memory limit exceeded |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Runtime error |
1387 ms |
65536 KB |
Execution killed with signal 9 |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Runtime error |
1643 ms |
65536 KB |
Execution killed with signal 9 |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Runtime error |
1828 ms |
65536 KB |
Execution killed with signal 9 |
| 2 |
Halted |
0 ms |
0 KB |
- |
