How To Find Duplicates In Array

Ritesh Singh

10y752Code

In an array 1-100 many numbers are duplicates, how do you find it?

private int[] ReturnduplicateElement(int[] a1)
{
    Hashtable objHashTable = new Hashtable();
    List<int> integerList = new List<int>();
    for (int i = 0; i < a1.Length ; i++)
    {
        if (objHashTable.ContainsKey(a1[i]))
        {
           integerList.Add(a1[i]);
        }
        else{ objHashTable.Add(a1[i], a1[i]); }
    }
    return integerList.ToArray();
}