Submission #1093041

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Source Code Expand

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef vector<int> vint;
typedef pair<int,int> pint;
typedef vector<pint> vpint;
#define rep(i,n) for(int i=0;i<(n);i++)
#define reps(i,f,n) for(int i=(f);i<(n);i++)
#define each(it,v) for(__typeof((v).begin()) it=(v).begin();it!=(v).end();it++)
#define all(v) (v).begin(),(v).end()
#define pb push_back
#define mp make_pair
#define fi first
#define se second
#define chmax(a, b) a = (((a)<(b)) ? (b) : (a))
#define chmin(a, b) a = (((a)>(b)) ? (b) : (a))
const int MOD = 1e9 + 7;
const int INF = 1e9;

ll a[100010];
int main(void){
	int n; cin >> n;
	set<ll> se;
	// ll sum = 0;
	rep(i, n){
		cin >> a[i];
		se.insert(a[i]);
	}
	if(se.size() != n){
		printf("NO\n");
		return 0;
	}

	ll sum = 0;
	set<ll> tt;
	rep(i, n - 1){
		sum += a[i + 1] - a[i];
		tt.insert(a[i + 1] - a[i]);
	}
	sum += a[0] - a[n - 1];
	tt.insert(a[0] - a[n - 1]);
	if(tt.size() != 2){
		printf("NO\n");
		return 0;
	}
	if(sum == 0){
		printf("YES\n");
	}else{
		printf("NO\n");
	}
	return 0;
}

Submission Info

Judge Result