#include <bits/stdc++.h>
#define ll long long
#define ld long double
#define pb push_back
#define fi first
#define se second
#define mp make_pair
#define all(x) x.begin(),x.end()
#define rall(x) x.rbegin(),x.rend()
#define pii pair<int,int>
#define pll pair<ll,ll>
#define en '\n'
#define sp ' '
#define smin(a, b) a = min(a, b)
#define smax(a, b) a = max(a, b)
#define sadd(a, b) a = add(a, b)
#define ssub(a, b) a = sub(a, b)
#define smul(a, b) a = mul(a, b)
#define sdvs(a, b) a = dvs(a, b)
#define ar array
#define yes cout<<"YES\n"
#define no cout<<"NO\n"
#define bitcnt(x) __builtin_popcount(x)
#define cur dp[i][sum]
using namespace std;
const ll mod = (1 ? 1e9 + 7 : 998244353);
const int N = 2e5 + 2;
const int M = 2e7 + 2;
const int inf = 2e9;
const ll linf = 1e18;
/*ll g(ll a){a=(a+mod)%mod; return a;}
ll add(ll a,ll b){a+=b;return a>=mod?a-mod:a;}
ll sub(ll a, ll b){a+=mod-b;return a>=mod?a-mod:a;}
ll mul(ll a,ll b){return a*b%mod;}
ll exp(ll x,ll k){ll ans=1;for(;k;k>>=1,x=mul(x,x))if(k&1)ans=mul(ans,x);return ans;}
ll inv(ll x){return exp(x,mod-2);}
ll dvs(ll a,ll b){return mul(a,inv(b));}*/
void solve(){
    int n,m;
    cin>>n>>m;
    vector<array<int,2>>a;
    for(int i=0;i<n;i++){
        for(int j=0;j<m;j++){
            int x;
            cin >> x;
            a.pb({x,i});
        }
    }
    sort(all(a));
    vector<vector<int>>ans(n,vector<int>(m,0));
    for(int j=0;j<m;j++){
        ans[a[j][1]][j]=a[j][0];
    }
    for(int j=m;j<n*m;j++){
        int whe = a[j][1];
        int wha = a[j][0];
        for(int i=0;i<m;i++){
            if(!ans[whe][i]){
                ans[whe][i]=wha;
                break;
            }
        }
    }
    for(int i=0;i<n;i++){
        for(int j=0;j<m;j++){
            cout << ans[i][j] << sp;
        }
        cout << en;
    }
}
int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    cerr.tie(0);
    int t = 1;
    cin >> t;
    while(t--)solve();
    return 0;
}
