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Create an Array of Random Numbers whose sum is < X

Posted on 2010-11-20
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Last Modified: 2012-05-10
How would I go about creating a 1 dimensional array with N elements,
whose sum < X?

thx
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Question by:JustinW
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6 Comments
 
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Author Comment

by:JustinW
Comment Utility
and the random numbers are integers between
0 and Z
0
 
LVL 35

Expert Comment

by:Miguel Oz
Comment Utility
See attached code
public int[] GetRandomArray(int max, int sumMax, int size)

        {

            Debug.Assert(sumMax >= max, "Invalid usage");

            Debug.Assert(max > 0, "Invalid usage");

            Debug.Assert(size > 0, "Invalid usage");

            Random r = new Random();

            List<int> result = new List<int>(size);

            int sum = 0;

            for (int i = 0; i < size; i++)

            {

                result[i] = r.Next(max+1);

                sum = result[i] + sum;

            }

            while (sum > sumMax)

            {

                sum = 0;

                for (int i = 0; i < size; i++)

                {

                    if (result[i] > 0)

                        result[i] = result[i] > 0 ? (result[i] - 1): 0;

                }

            }

            return result.ToArray();

        }

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LVL 35

Accepted Solution

by:
Miguel Oz earned 500 total points
Comment Utility
where maxSum = X
maxValue=Z
size=N
public int[] GetRandomArray(int maxValue, int maxSum, int size)

        {

            Debug.Assert(maxSum >= maxValue, "Invalid usage");

            Debug.Assert(maxValue > 0, "Invalid usage");

            Debug.Assert(size > 0, "Invalid usage");

            Random r = new Random();

            List<int> result = new List<int>(size);

            int sum = 0;

            for (int i = 0; i < size; i++)

            {

                result[i] = r.Next(0,maxValue);

                sum = result[i] + sum;

            }

            while (sum > maxSum)

            {

                sum = 0;

                for (int i = 0; i < size; i++)

                {

                    if (result[i] > 0)

                        result[i] = result[i] > 0 ? (result[i] - 1): 0;

                }

            }

            return result.ToArray();

        }

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LVL 1

Author Closing Comment

by:JustinW
Comment Utility
very nice;
danke
0
 
LVL 1

Author Comment

by:JustinW
Comment Utility
Here's my crack at it in ruby
def rnd_rng(leng, the_max)

  arr = Array.new(leng){0}

  the_max = rand(the_max)



  i = 0

  while the_max > 0 && i <leng do

    tmp = rand(the_max)

    arr[i] = tmp

    the_max = the_max - tmp

    i +=1

  end



  return arr.shuffle!

end

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LVL 35

Expert Comment

by:Miguel Oz
Comment Utility
and vb.net version is:
Public Function GetRandomArray(maxValue As Integer, maxSum As Integer, size As Integer) As Integer()

	Debug.Assert(maxSum >= maxValue, "Invalid usage")

	Debug.Assert(maxValue > 0, "Invalid usage")

	Debug.Assert(size > 0, "Invalid usage")

	Dim r As New Random()

	Dim result As New List(Of Integer)(size)

	Dim sum As Integer = 0

	For i As Integer = 0 To size - 1

		result(i) = r.[Next](0, maxValue)

		sum = result(i) + sum

	Next

	While sum > maxSum

		sum = 0

		For i As Integer = 0 To size - 1

			If result(i) > 0 Then

				result(i) = If(result(i) > 0, (result(i) - 1), 0)

			End If

		Next

	End While

	Return result.ToArray()

End Function

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