CONNECT C++

#include<bits/stdc++.h>
using namespace std;

int cha[100005]= {0};
int n,m,s;
vector<int> a[100005];
int res=0;

void dfs(int u)
{
    cout<<u<<" ";
    //printf("%d ",u);
    for(int i=0; i<a[u].size(); i++)
    {
        int v=a[u][i];
        if(cha[v]==0)
        {
            cha[v]=u;
            dfs(v);
        }
    }
}
void nhap()
{
    //scanf("%d %d",&n,&m);
    cin>>n>>m;
    int x,y;
    for(int i=1; i<=m; i++)
    {
        //scanf("%d %d",&x,&y);
        cin>>x>>y;
        a[x].push_back(y);
        a[y].push_back(x);
    }

}
void giai()
{
    for(int i=1;i<=n;i++)
    {
        if(cha[i]==0)
        {
            cha[i]=n+1;
            dfs(i);
            //printf("\n")
            ;cout<<endl;
        }

    }
}
int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);

    freopen("connect.inp","r",stdin);
    freopen("connect.out","w",stdout);
    nhap();
    giai();
}