1826B - Lunatic Never Content - CodeForces Solution

/*
 VINAY SAGAR
*/
#include <bits/stdc++.h>
using namespace std;

#define int long long
#define v vector<int> 
#define en endl
#define l1 1e6
#define all(v) v.begin(), v.end()
#define rall(v) v.rbegin(), v.rend()
#define pb push_back
#define sz(a) (int)a.size()
#define loop(ii, n) for (int ii = 0; ii < n; ii++)

const int MOD = 1e9 + 8;
const int N = 1e5+10;

void solve()
{
    int n; cin>>n;

    vector<int> v1;
    loop(i,n)
    {
        int x; cin>>x;
        v1.pb(x);
    }
    

    // int t = abs(v1[n-1]-v1[0]);
    int g = 0;

    loop(i,n/2)
    {
        
       g = __gcd(g,abs(v1[n-i-1]-v1[i]));
    
    }

    cout<<g<<endl;

    

}
int32_t main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    int t;
    cin >> t;
    while (t--)
    {
        solve();

    }
}