#include <bits/stdc++.h>
using namespace std;
// #include <ext/pb_ds/assoc_container.hpp>
// #include <ext/pb_ds/tree_policy.hpp>
// using namespace __gnu_pbds;

template <typename A, typename B>
string to_string(pair<A, B> p)
{
    return "(" + to_string(p.first) + ", " + to_string(p.second) + ")";
}
template <size_t N>
string to_string(bitset<N> v)
{
    string res = "";
    for (size_t i = 0; i < N; i++)
    {
        res += static_cast<char>('0' + v[i]);
    }
    return res;
}
template <typename A>
string to_string(A v)
{
    bool first = true;
    string res = "{";
    for (const auto &x : v)
    {
        if (!first)
        {
            res += ", ";
        }
        first = false;
        res += to_string(x);
    }
    res += "}";
    return res;
}

int dx[] = {-1, 0, 1, 0};
int dy[] = {0, 1, 0, -1};
//   cout << fixed << setprecision(10);
#define rep(i, a, b) for (int i = a; i < (b); ++i)
#define per(i, a, b) for (int i = (a)-1; i >= (b); i--)
#define forn(i, n) rep(i, 0, n)
#define rof(i, n) per(i, n, 0)
#define dbg(x) cout << #x << "=" << x << endl
#define dbg2(x, y) cout << #x << "=" << x << "," << #y << "=" << y << endl
#define dbg3(x, y, z) cout << #x << "=" << x << "," << #y << "=" << y << "," << #z << "=" << z << endl
#define ff first
#define ss second
#define mp make_pair
#define all(x) (x).begin(), (x).end()
#define endl "\n"
#define int long long
#define ll long long
#define pb push_back
#define pii pair<int, int>
#define setbits(x) __builtin_popcountll(x)
#define zerbefone(x) __builtin_ctzll(x)
#define pqb priority_queue<int>                               // maxheap
#define pqs priority_queue<int, vector<int>, greater<int>>    // minheap
#define piipqs priority_queue<pii, vector<pii>, greater<pii>> // minheap for pair<int,int>
#define piipqb priority_queue<pii>                            // maxheap for pair<int,int>
#define mod 1000000007
#define inf 100000000000000000 //1e17
#define mem0(a) memset(a, 0, sizeof(a))
#define mem1(a) memset(a, -1, sizeof(a))
#define meminf(a) memset(a, 0x7f, sizeof(a))
#define precise(x, y) fixed << setprecision(y) << x
#define FIO                       \
    ios_base::sync_with_stdio(0); \
    cin.tie(0);                   \
    cout.tie(0)
#define yes cout << "YES" << endl
#define no cout << "NO" << endl
// #define oset            tree<int, null_type,less<int>, rb_tree_tag,tree_order_statistics_node_update>
mt19937_64 rng(std::chrono::steady_clock::now().time_since_epoch().count());
// mt19937_64 rng(61378913);
/* usage - just do rng() */

template <typename T, typename T1>
T amax(T &a, T1 b)
{
    if (b > a)
        a = b;
    return a;
}
template <typename T, typename T1>
T amin(T &a, T1 b)
{
    if (b < a)
        a = b;
    return a;
}

ll add(ll a, ll b)
{
    a += b;
    if (a >= mod)
        a -= mod;
    return a;
}

ll sub(ll a, ll b)
{
    a -= b;
    if (a < 0)
        a += mod;
    return a;
}

ll mul(ll a, ll b)
{
    return (a * b) % mod;
}

// *************************** Code Begins **************************** //

void solve()
{
    int n, m;
    cin >> n >> m;
    vector<pii> arr;
    for (int i = 0; i < n; i++)
    {
        for (int j = 0; j < m; j++)
        {
            int x;
            cin >> x;
            arr.pb(mp(x, i));
        }
    }
    sort(all(arr));
    vector<vector<int>> ans(n, vector<int>(m, -1));
    for (int i = 0; i < m; i++)
    {
        ans[arr[i].ss][i] = arr[i].ff;
    }

    int j = 0;
    int i = m;
    while (i < m * n)
    {
        if (ans[arr[i].ss][j % m] == -1)
        {
            ans[arr[i].ss][j % m] = arr[i].ff;
            i++;
        }
        else
            j++;
    }

    for (int i = 0; i < n; i++)
    {
        for (auto x : ans[i])
            cout << x << " ";
        cout << endl;
    }
}

signed main()
{
    FIO;
    int tt = 1;
    cin >> tt;
    for (int i = 1; i <= tt; i++)
        solve();
}