Find intersection of two unsorted arrays?

Question

Sigiloso · Accepted Answer

Two ways.
Sort both arrays. Use pointers to traverse both the arrays from start and print any matching elements.
Or
Use Hashmap storing the array element and its count value from first array.

Sigiloso · Answer

Since Amazon is particularly fond of hash tables, I'd prefer to use it in the solution. Plus it's slightly faster than sorting both arrays.

        public static int[] ArrayIntersection(int[] arr1, int[] arr2)
        {
            Dictionary hashTable = new Dictionary();

            for (int i = 0; i  list = new List();

            for (int i = 0; i < arr2.Length; i++)
            {
                if (hashTable.ContainsKey(arr2[i]))
                {
                    list.Add(arr2[i]);
                }
            }

            return list.ToArray();
        }

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