bfs in C++
// A Quick implementation of BFS using
// vectors and queue
#include <bits/stdc++.h>
#define pb push_back
using namespace std;
vector<bool> v;
vector<vector<int> > g;
void edge(int a, int b)
{
g[a].pb(b);
// for undirected graph add this line
// g[b].pb(a);
}
void bfs(int u)
{
queue<int> q;
q.push(u);
v[u] = true;
while (!q.empty()) {
int f = q.front();
q.pop();
cout << f << " ";
// Enqueue all adjacent of f and mark them visited
for (auto i = g[f].begin(); i != g[f].end(); i++) {
if (!v[*i]) {
q.push(*i);
v[*i] = true;
}
}
}
}
// Driver code
int main()
{
int n, e;
cin >> n >> e;
v.assign(n, false);
g.assign(n, vector<int>());
int a, b;
for (int i = 0; i < e; i++) {
cin >> a >> b;
edge(a, b);
}
for (int i = 0; i < n; i++) {
if (!v[i])
bfs(i);
}
return 0;
}