Chef and Minimum Colouring

#include<bits/stdc++.h>
#define ll long long int
const ll M=1e9+7;
using namespace std;
vector<ll>v[100005];
ll ans,m;
void solve(ll p,ll mn,ll mx){
    //printf("%lld %lld %lld\n",p,mn,mx);
    if (p==m){
        ans=min(ans,mx-mn);
        return;
    }
    ll mx1=upper_bound(v[p].begin(),v[p].end(),mx)-v[p].begin()-1;
    if (mx1<0) mx1++;
    if (mn<=v[p][mx1] && v[p][mx1]<=mx){
        solve(p+1,mn,mx);
        return;
    }

    if (v[p][mx1]<mx) mx1++;
    ll mn1=upper_bound(v[p].begin(),v[p].end(),mn)-v[p].begin()-1;
    if (mn1<0) mn1++;
    //printf("mn1=%lld mx1=%lld\n",mn1,mx1);

    if (mx1>=v[p].size()) solve(p+1,v[p][mn1],mx);
    else{
        if (mn<v[p][mn1] || v[p][mx1]-mx < mn-v[p][mn1])
             solve(p+1,mn,v[p][mx1]);
        else if(v[p][mx1]-mx == mn-v[p][mn1]){
            solve(p+1,v[p][mn1],mx);
            solve(p+1,mn,v[p][mx1]);
        }
        else solve(p+1,v[p][mn1],mx);
    }
    return;
}
int main(){
//  freopen("in.txt","r",stdin);
//  freopen("out.txt","w",stdout);
    ios_base::sync_with_stdio(0);
    cin.tie(0),cout.tie(0);
    ll t,n,i,x;
    cin>>t;
    while(cin>>n>>m){
        for (i=0; i<m; i++)v[i].clear();
        for (i=0; i<n; i++){
            cin>>x;
            v[i%m].push_back(x);
        }
        for (i=0; i<m; i++)
            sort(v[i].begin(),v[i].end());
//      for (i=0; i<m; i++){
//          for (int j=0; j<v[i].size(); j++)
//              printf("%lld ",v[i][j]);
//          puts("");
//      }
        ans=1e9;
        for (i=0; i<v[0].size(); i++)
            solve(1,v[0][i],v[0][i]);
        cout<<ans<<endl;
    }
    return 0;
}