M Random Numbers Which Sum To N

 1 static void Main()
 2 {
 3     int count = 30;
 4     int[] numbers = getNumbers(count, 155);
 5     for (int index = 0; index < count; index++)
 6     {
 7         Console.Write(numbers[index]);
 8         if ((index + 1) % 10 == 0)
 9             Console.WriteLine("");
10         else if (index != count - 1)
11             Console.Write(",");
12     }
13     Console.ReadKey();
14 }
15 static int[] getNumbers(int count, int total)
16 {
17     const int LOWERBOUND = 1;
18     const int UPPERBOUND = 9;
19 
20     int[] result = new int[count];
21     int currentsum = 0;
22     int low, high, calc;
23     
24     if((UPPERBOUND * count) < total ||
25         (LOWERBOUND * count) > total ||
26         UPPERBOUND < LOWERBOUND)
27         throw new Exception("Not possible.");
28 
29     Random rnd = new Random();
30 
31     for (int index = 0; index < count; index++)
32     {
33         calc = (total - currentsum) - (UPPERBOUND * (count - 1 - index));
34         low = calc < LOWERBOUND ? LOWERBOUND : calc;
35         calc = (total - currentsum) - (LOWERBOUND * (count - 1 - index));
36         high = calc > UPPERBOUND ? UPPERBOUND : calc;
37 
38         result[index] = rnd.Next(low, high + 1);
39 
40         currentsum += result[index];
41     }
42 
43     // The tail numbers are going to drift up or down so we should shuffle the results.
44 
45     int shuffleCount = rnd.Next(count * 5, count * 10);
46     while (shuffleCount-- > 0)
47         swap(ref result[rnd.Next(0, count)], ref result[rnd.Next(0, count)]);
48 
49     return result;
50 }
51 public static void swap(ref int item1, ref int item2)
52 {
53     int temp = item1;
54     item1 = item2;
55     item2 = temp;
56 }