1658C - Shinju and the Lost Permutation - CodeForces Solution

/**
 *   ^~^  ,
 *  ('Y') )
 *  /   \/ 
 * (\|||/)
**/
 
#include <iostream>
#include <cstdio>
#include <algorithm>
#include <vector>
#include <bitset>
#include <set>
#include <unordered_set>
#include <numeric>
#include <map>
#include <unordered_map>
#include <string>
#include <cmath>
#include <tuple>
#include <queue>
#include <stack>
#include <cassert>
#include <random>
#include <array>
using namespace std; 
 
#define ll long long
#define log(...) logger(#__VA_ARGS__, __VA_ARGS__)
template<class T, class ...Vals>
void logger(T names, Vals&&... values){
    cout << names << " = ";
    string delimiter = "";
    (..., (cout << delimiter << values, delimiter = ", "));
    cout << '\n';
}
 
const int INF = 0x7FFFFFFF;
const int MINF = 0x80000000;
const int MOD = 1e9+7;
// const int MOD = 998244353;

// ios_base::sync_with_stdio(0); 
// cin.tie(0);

template<class T, class U> void logv(vector<pair<T,U>> x){
    for (int i = 0; i < x.size(); i++){
        cout << x[i].first << " " << x[i].second << '\n';
    }
}
 
template<class T> void logv(vector<T> x){
    for (int i = 0; i < x.size(); i++){
        cout << x[i] << " ";
    }
    cout << '\n';
}

void solve(){
    int n; cin >> n;
    vector<int> a(n);
    for (auto &A : a) cin >> A;
    int ones=0, ens=0;
    for(int i = 0; i < n; i++){
        ones += a[i]==1;
        ens += a[i]==n;
    }
    if (ones!=1){
        cout << "NO\n";
        return;
    }
    if (ens>1){
        cout << "NO\n";
        return;
    }
    for (int i = 0; i < n; i++){
        if(a[i]-a[(i-1+n)%n]>1){
            cout << "NO\n";
            return;
        }
    }
    cout << "YES\n";
}

int main(){
    int t; cin >> t;
    while(t--){
        solve();
    }
}