using System;
using System.Collections.Generic;
using System.Linq;
/*
Select N unique random indices from an existing array in C#.
Return the indices and print both the index and the corresponding value.
Approach:
- Build a list of indices: 0, 1, 2, ..., size-1.
- Shuffle the list using Random + OrderBy.
- Take the first N shuffled indices — guaranteed unique.
- Return those indices to the caller.
*/
class UniqueRandomIndices
{
// Return N unique random indices
static List<int> PickUniqueIndices(int arraySize, int count)
{
if (count > arraySize)
throw new ArgumentException("Cannot pick more unique indices than array size.");
// Build index list
List<int> indices = new List<int>(arraySize);
for (int i = 0; i < arraySize; i++)
indices.Add(i);
// Shuffle indices
Random rng = new Random();
indices = indices.OrderBy(x => rng.Next()).ToList();
// Return first N indices
return indices.Take(count).ToList();
}
static void Main()
{
// Example array
int[] data = {5, 12, 5, 19, 5, 33, 47, 5, 58, 61, 17, 3, 5, 74, 83, 90, 6};
int N = 6; // number of unique indices to pick
// Get unique random indices
List<int> indices = PickUniqueIndices(data.Length, N);
// Print results
Console.WriteLine("Random unique indices and their values:");
foreach (int idx in indices)
{
Console.WriteLine("index " + idx + " -> value " + data[idx]);
}
}
}
/*
run:
Random unique indices and their values:
index 7 -> value 5
index 2 -> value 5
index 11 -> value 3
index 5 -> value 33
index 4 -> value 5
index 14 -> value 83
*/
