Question

Basically I have and array of integers that vary in size. I need to compare each number to each other number and display which number is repeated. For example:

Dim ints() As Integer = {1,2,2,5,4,6}

The number that shows up more than once is 2.

How can I run through the array and compare each integer with the numbers in the array. I tried a for loop but it didn’t return the value I was looking for. I am new to VB.NET and do not understand fully.

Answer 1

Dim ints() As Integer = {1,2,2,5,4,6}

Dim repeatedNumbers = ints.GroupBy(Function(intValue) intValue) _
                          .Where(Function(grp) grp.Count > 1)

For each grp in repeatedNumbers
    Console.WriteLine("Number {0} is repeated {1} times", grp(0), grp.Count)
Next

What this code does:

• We first call GroupBy, which groups items by their value. The Function gets the grouping key, in this case we simply group by the array’s value itself. This call returns a sequence of
  groups. There is one group for every unique value in the array. The
  group contains all items that correspond to a unique value. So if a value appears twice in the array, there will be a group which contains two ints with this value.
• We call Where to filter groups. We only want groups for which the count is greater than one, so that only duplicate values are considered.
• We then loop through the result. grp(0) gives us the first number in the group (we could have picked any number in the group, since all numbers in a group are the same!) and the Count property gives us the number of repetitions.