BFS graphs using edges

#include <bits/stdc++.h> 

void prepareAdjList(unordered_map<int, set<int>> &adj, vector<pair<int,int>> &edges){
    for(int i=0;i<edges.size();i++){
        int u = edges[i].first;
        int v = edges[i].second;
        
        adj[u].insert(v);
        adj[v].insert(u);
    }
}
void bfs(unordered_map<int, set<int>> &adj, unordered_map<int, bool> &vis, vector<int> &ans,
        int node){
    queue<int> q;
    q.push(node);
    vis[node] = 1;
    while(!q.empty()){
        int frontNode = q.front();
        q.pop();
        ans.push_back(frontNode);
        for(auto it:adj[frontNode]){
            if(!vis[it]){
                q.push(it);
                vis[it] = 1;
            }
        }
    }
}
vector<int> BFS(int vertex, vector<pair<int, int>> edges)
{
    unordered_map<int, set<int>> adj;
    vector<int> ans;
    unordered_map<int, bool> vis;
    prepareAdjList(adj, edges);
    //traverse all component of graph
    for(int i=0;i<vertex;i++){
        if(!vis[i]){
            bfs(adj,vis,ans,i);
        }
    }
    return ans;
}