JLY-Editorial

The idea is to maintain a boolean array to store set of absolute difference of successive elements.
a) If absolute difference between two elements is more than n-1 or 0, return false.
b) If an absolute difference repeated, then all absolute differences from 1 to n-1 can’t be present Pigeon Hole Principle, return false.

#include<bits stdc++.h="">
using namespace std;
set<int> S;
int A[1000001];
int main(){
    int t ;
    cin >> t ;
    while(t--){
        int N ;
        cin >> N ;
        for(int i = 1 ; i<= N  ; i++) cin >> A[i];
        for(int i = 2 ; i<= N ; i++){
            S.insert(abs(A[i] - A[i-1]));
        }
        if(S.size() == N - 1) {
            int ind = 1;
            bool found = true ;
            for(auto it = S.begin() ; it!= S.end() ; it++ , ind++){
                if(*it != ind) {
                    found = false ;
                    break;
                }
            }
            if(found)          cout << "Jolly";
            else
            cout << "Not Jolly";
        }
        else
            cout << "Not Jolly";
        S.clear();
    }
}