Problem:
Score : 300 points

Problem Statement

Given is a sequence of integers A_1, A_2, ..., A_N.
If its elements are pairwise distinct, print YES; otherwise, print NO.

Constraints

2 ≤ N ≤ 200000

1 ≤ A_i ≤ 10^9

All values in input are integers.

Input

Input is given from Standard Input in the following format:

N
A_1 ... A_N

Output

If the elements of the sequence are pairwise distinct, print YES; otherwise, print NO.

Sample Input 1

5
2 6 1 4 5

Sample Output 1

YES

The elements are pairwise distinct.

Sample Input 2

6
4 1 3 1 6 2

Sample Output 2

NO

The second and fourth elements are identical.

Sample Input 3

2
10000000 10000000

Sample Output 3

NO

Solution in Scala (2.11.7) (judge verdict: Accepted)

object Main {
  def main(args: Array[String]): Unit = {
    val sc = new java.util.Scanner(System.in)
    val length = sc.nextInt()
    val input = Array.fill(length)(sc.nextInt())

    val hasDuplicateValue = input.sorted
      .foldLeft((false, 0)) { (memo, value) =>
        val ans = if (memo._1) {
          true
        } else {
          memo._2 == value
        }
        (ans, value)
      }
      ._1

    val ans = if (hasDuplicateValue) "NO" else "YES"
    println(ans)
  }
}