D

#include <iostream>
#include <cstdio>
#include <array>
#define task "tests"
using namespace std;
using ll = long long;
using ld = long double;

const int N = 1 << 20 + 2;
const int Inf = 1e9 + 7;
int k, n;
int a[N];
int all;
int par[N];
int dp[N], g[N];

void Read(){
    cin >> k >> n;
    for(int i = 1; i <= n; ++i){
        string s;
        cin >> s;
        a[i] = 0;
        for(int j = 0; j < k; ++j)
            if(s[j] == '0')
                a[i] |= 1 << j;
        ++g[a[i]];
    }
}

void Calculate_g(){
    all = (1 << k) - 1;
    for(int i = 0; i <= all; ++i)
        dp[i] = Inf,
        par[i] = -1;
    for(int j = 0; j < k; ++j)
        for(int i = 0; i < (1 << k); ++i)
            if(i & (1 << j))
                g[i] += g[i ^ (1 << j)];
}

void Trace(int v){
    if(par[v] == -1)
        return;
    Trace(par[v]);
    int vv = (v ^ par[v]), lv = 0;
    while(vv > 1){
        ++lv;
        vv >>= 1;
    }
    cout << lv + 1 << " ";
}

void Solve(){
    dp[0] = 0;
    for(int i = 1; i < (1 << k); ++i)
        for(int j = 0; j < k; ++j)
            if(i & (1 << j))
                if(dp[i] >= dp[i ^ (1 << j)] + g[all ^ (i ^ (1 << j))]){
                    dp[i] = dp[i ^ (1 << j)] + g[all ^ (i ^ (1 << j))];
                    par[i] = i ^ (1 << j);
                }
    cout << dp[(1 << k) - 1] << "\n";
    Trace((1 << k) - 1);
}

main(){
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0); if(fopen(task".IN", "r"))
    freopen(task".IN", "r", stdin);
    int t;
    cin >> t;
    while(t--)
        Read(),
        Calculate_g(),
        Solve();
}