UVa1594 - Ducci Sequence

#include<iostream>
#include<vector>
#include<cmath>
#include<algorithm>
using namespace std;
vector<int> a;
bool is_zero(int t)
{

    for(int i=0;i<1009;i++){
        int p=a[0],j=0,q=0;
        for(;j<t-1;j++){
            a[j] = abs(a[j] - a[j+1]);
            if( a[j]==0 )q++;
        }
        if( ( a[j]=abs(a[j]-p) ) == 0 )q++;
        if(q == t) return true;
    }
    return false;
}
int main()
{
    int n;
    cin>>n;
    while(n--){
        int t;
        cin>>t;
        for(int i=0;i<t;i++){
                int x;
                cin>>x;
                a.push_back(x);
        }
        if(is_zero(t)) cout<<"ZERO\n";
            else cout<<"LOOP\n";
        a.clear();
    }
    return 0;
}