图的遍历之DFS，BFS

#include <bits/stdc++.h>
using namespace std;
int a[105][105], t = 0, b[105], c[105];
void DFS(int k, int n)
{
    int i;
    c[t++] = k;
    b[k] = 1;
    for(i = 0; i<n; i++)
    {
        if(a[k][i] == 1 && b[i]==0)
        {
            DFS(i, n);
        }
    }
    return;
}
/*void BFS(int k, int n)
{
    queue<int>q;
    int i;
    q.push(k);
    b[k] = 1;
    while(!q.empty())
    {
        int s = q.front();
        cout<<s<<endl;
        for(i = 0; i<n; i++)
        {
            if(a[s][i] == 1 && b[i] == 0)
            {
                q.push(i);
                b[i] = 1;
            }
        }
        q.pop();
    }
}*/
int main()
{
    int i, n, m, x, y, T, k, j;
    cin>>T;
    while(T!=0)
    {
        cin>>n>>m;
        t = 0;
        memset(b,0,sizeof(b));
        memset(a,0,sizeof(a));
        memset(c,0,sizeof(c));
        for(i = 0; i<m; i++)
        {
            cin>>x>>y;
            a[x][y] = a[y][x] = 1;
        }
        for(i = 0; i<n; i++)
        {
            for( j = 0; j<n; j++)
            {
                if(a[i][j] == 1)
                {
                    k = i;
                    break;
                }
            }
            if(j<n) break;
        }
        DFS(k, n);
        for(i = 0; i<n; i++)
        {
            if(i!=n-1) printf("%d ", c[i]);
            else printf("%d\n", c[i]);
        }
        T--;
    }
    return 0;
}