using System;
using System.Collections.Generic;
using System.Linq;
//Google Question
//Given an array = [2,5,1,2,3,5,1,2,4]:
//It should return 2
//Given an array = [2,1,1,2,3,5,1,2,4]:
//It should return 1
//Given an array = [2,3,4,5]:
//It should return undefined
class MainClass {
static void Main() {
Console.WriteLine(GetRecurringCharacter(firstArray));
Console.WriteLine(GetRecurringCharacter(secondArray));
Console.WriteLine(GetRecurringCharacter(thirdArray));
}
static int[] firstArray = { 2,5,1,2,3,5,1,2,4 };
static int[] secondArray = { 2,1,1,2,3,5,1,2,4 };
static int[] thirdArray = { 2,3,4,5 };
private static int GetRecurringCharacter(int[] array)
{
HashSet<int> seenCharacters = new HashSet<int>();
foreach (var character in array) {
if (seenCharacters.Contains(character))
{
return character;
} else {
seenCharacters.Add(character);
}
}
return -1;
}
}
