#include<bits/stdc++.h>

#define LL long long

#define fi first

#define se second

#define mk make_pair

#define PLL pair<LL, LL>

#define PLI pair<LL, int>

#define PII pair<int, int>

#define SZ(x) ((int)x.size())

#define ull unsigned long long

using namespace std;

const int N = 2e5 + ;

const int inf = 0x3f3f3f3f;

const LL INF = 0x3f3f3f3f3f3f3f3f;

const int mod = 1e9 + ;

const double eps = 1e-;

const double PI = acos(-);

int T, m, n, up, dp2[<<], dp[<<], pre[<<];

char s[];

vector<int> ans;

int main() {

//    freopen("tests.in", "r", stdin);

    scanf("%d", &T);

    while(T--) {

        ans.clear();

        scanf("%d%d", &m, &n);

        up =  << m;

        for(int i = ; i < up; i++) dp2[i] = , dp[i] = inf;

        for(int i = ; i < n; i++) {

            scanf("%s", s); int x = ;

            for(int j = ; j < m; j++)

                if(s[j] == '') x +=  << j;

            dp2[x]++;

        }

        for(int i = ; i < m; i++)

            for(int s = ; s < up; s++)

                if(s>>i&) dp2[s^(<<i)] += dp2[s];

        dp[] = ;

        for(int s = ; s < up; s++) {

            for(int i = ; i < m; i++) {

                if(s>>i&) continue;

                int nexs = s | (<<i);

                if(dp[s]+dp2[s] < dp[nexs]) {

                    dp[nexs] = dp[s]+dp2[s];

                    pre[nexs] = s;

                }

            }

        }

        int nows = up-, nexs;

        while(nows) {

            nexs = pre[nows];

            int xo = nexs ^ nows;

            for(int i = ; i < m; i++) {

                if(<<i == xo) {

                    ans.push_back(i+);

                    break;

                }

            }

            nows = nexs;

        }

        reverse(ans.begin(), ans.end());

        printf("%d\n", dp[up-]);

        for(int t : ans) printf("%d ", t);

        puts("");

    }

    return ;

}

/*

*/