EN
C#/.NET - generate unique random numbers
12 points
There is couple of ways to generate unique random numbers in C#/.NET.
xxxxxxxxxx1
public static class RandomUtils2
{3
public static int[] generateUniqueNumbers(int minValue, int maxValue)4
{5
if (minValue > maxValue)6
throw new ArgumentException("Minimal value cannot be bigger than maximal value.");7
8
int[] values = new int[maxValue - minValue + 1];9
10
for (int i = 0; i < values.Length; ++i)11
values[i] = minValue + i;12
13
Random random = new Random();14
15
for (int i = 0; i < values.Length; ++i)16
{17
int index = random.Next(values.Length);18
19
if (i == index)20
continue;21
22
int tmp = values[i];23
24
values[i] = values[index];25
values[index] = tmp;26
}27
28
return values;29
}30
}Example:
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int[] ranges = {2
// min, max,3
5, 15,4
-4, 45
};6
7
for(int i = 0; i < ranges.Length; i += 2)8
{9
int minValue = ranges[i + 0];10
int maxValue = ranges[i + 1];11
12
int[] values = RandomUtils.generateUniqueNumbers(minValue, maxValue);13
14
Console.WriteLine("Random unique values from " + minValue + " to " + maxValue + ": ");15
16
foreach (int entry in values)17
Console.Write(entry + " ");18
19
Console.WriteLine();20
Console.WriteLine();21
}Output:
xxxxxxxxxx1
Random unique values from 5 to 15:2
14 8 15 7 5 6 10 9 13 11 123
4
Random unique values from -4 to +4:5
0 -4 4 1 -3 2 3 -1 -2xxxxxxxxxx1
public static class RandomUtils2
{3
public static int[] generateUniqueNumbers(int minValue, int maxValue)4
{5
if (minValue > maxValue)6
throw new ArgumentException("Minimal value cannot be bigger than maximal value.");7
8
int[] values = new int[maxValue - minValue + 1];9
10
for (int i = 0; i < values.Length; ++i)11
values[i] = minValue + i;12
13
Random random = new Random();14
15
Array.Sort(values, (a, b) => random.Next(-1, 2));16
17
return values;18
}19
}Example:
xxxxxxxxxx1
int[] ranges = {2
// min, max,3
5, 15,4
-4, 45
};6
7
for(int i = 0; i < ranges.Length; i += 2)8
{9
int minValue = ranges[i + 0];10
int maxValue = ranges[i + 1];11
12
int[] values = RandomUtils.generateUniqueNumbers(minValue, maxValue);13
14
Console.WriteLine("Random unique values from " + minValue + " to " + maxValue + ": ");15
16
foreach (int entry in values)17
Console.Write(entry + " ");18
19
Console.WriteLine();20
Console.WriteLine();21
}Output:
xxxxxxxxxx1
Random unique values from 5 to 15:2
6 5 7 10 8 11 9 12 13 14 153
4
Random unique values from -4 to 4:5
-3 -4 -2 1 -1 0 4 2 3xxxxxxxxxx1
public static class RandomUtils2
{3
public static int[] generateUniqueNumbers(int minValue, int maxValue)4
{5
if (minValue > maxValue)6
throw new ArgumentException("Minimal value cannot be bigger than maximal value.");7
8
Random random = new Random();9
10
int[] values = Enumerable.Range(minValue, maxValue - minValue + 1)11
.OrderBy((a) => random.Next(-1, 2))12
.ToArray();13
14
return values;15
}16
}Example:
xxxxxxxxxx1
int[] ranges = {2
// min, max,3
5, 15,4
-4, 45
};6
7
for(int i = 0; i < ranges.Length; i += 2)8
{9
int minValue = ranges[i + 0];10
int maxValue = ranges[i + 1];11
12
int[] values = RandomUtils.generateUniqueNumbers(minValue, maxValue);13
14
Console.WriteLine("Random unique values from " + minValue + " to " + maxValue + ": ");15
16
foreach (int entry in values)17
Console.Write(entry + " ");18
19
Console.WriteLine();20
Console.WriteLine();21
}Output:
xxxxxxxxxx1
Random unique values from 5 to 15:2
5 7 8 9 11 13 14 6 10 12 153
4
Random unique values from -4 to 4:5
-3 0 -2 -1 1 2 4 -4 3xxxxxxxxxx1
public static class RandomUtils2
{3
public static int[] generateUniqueNumbers(int minValue, int maxValue)4
{5
if (minValue > maxValue)6
throw new ArgumentException("Minimal value cannot be bigger than maximal value.");7
8
Random random = new Random();9
HashSet<int> values = new HashSet<int>(maxValue - minValue + 1);10
11
for (int i = minValue; i < maxValue;)12
{13
int value = random.Next(minValue, maxValue + 1);14
15
if(values.Add(value))16
i += 1;17
}18
19
return values.ToArray();20
}21
}Example:
xxxxxxxxxx1
int[] ranges = {2
// min, max,3
5, 15,4
-4, 45
};6
7
for(int i = 0; i < ranges.Length; i += 2)8
{9
int minValue = ranges[i + 0];10
int maxValue = ranges[i + 1];11
12
int[] values = RandomUtils.generateUniqueNumbers(minValue, maxValue);13
14
Console.WriteLine("Random unique values from " + minValue + " to " + maxValue + ": ");15
16
foreach (int entry in values)17
Console.Write(entry + " ");18
19
Console.WriteLine();20
Console.WriteLine();21
}Output:
xxxxxxxxxx1
Random unique values from 5 to 15:2
5 14 8 11 10 12 9 13 7 63
4
Random unique values from -4 to 4:5
1 -4 -2 2 3 0 -1 -3Note: generating random unique values with HashSet could take in most worse case much more iterations than number of expected numbers.