#include<bits/stdc++.h>
using namespace std;
const int N = 1e5 + 2;
int n, m;
int p[2][N];
int tin[N], fup[N], timer;
vector < pair < int, int > > g[N];
int dsu_get(int x, int v){
return p[x][v] == v ? v : p[x][v] = dsu_get(x, p[x][v]);
}
void dfs(int v, int pr = 0){
tin[v] = fup[v] = ++timer;
used[v] = true;
for(int i = 0; i < (int)g[v].size(); i++){
int to = g[v][i].first,
ind = g[v][i].second;
if(ind == pr){
continue;
}
if(!used[to]){
dfs(to, ind);
if(fup[to] > tin[v]){
cout << v << " " << to << "\n";
}
fup[v] = min(fup[v], fup[to]);
}
else{
fup[v] = min(fup[v], tin[to]);
}
}
}
int main(){
ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
cin >> n >> m;
for(int i = 1; i <= n; i++){
p[0][i] = p[1][i] = i;
}
for(int i = 1; i <= m; i++){
int x, y;
cin >> x >> y;
if(dsu_get(0, x) == dsu_get(0, y)){
if(dsu_get(1, x) == dsu_get(1, y)){
continue;
}
p[1][dsu_get(1, x)] = dsu_get(1, y);
}
else{
p[0][dsu_get(0, x)] = dsu_get(0, y);
}
g[x].push_back(make_pair(y, i));
g[y].push_back(make_pair(x, i));
}
for(int i = 1; i <= n; i++){
if(!used[i]){
dfs(i);
}
}
}
Compilation message
pipes.cpp: In function 'void dfs(int, int)':
pipes.cpp:20:5: error: 'used' was not declared in this scope
used[v] = true;
^~~~
pipes.cpp: In function 'int main()':
pipes.cpp:61:13: error: 'used' was not declared in this scope
if(!used[i]){
^~~~
