import Foundation
/*
Select N unique random indices from an existing array in Swift.
Return the indices and print both the index and the corresponding value.
Approach:
- Build an array of indices: 0, 1, 2, ..., size-1.
- Shuffle the indices using shuffled() (Fisher–Yates internally).
- Take the first N shuffled indices — guaranteed unique.
- Return those indices to the caller.
*/
/** Return N unique random indices */
func pickUniqueIndices(arraySize: Int, count: Int) -> [Int] {
if count > arraySize {
fatalError("Cannot pick more unique indices than array size.")
}
// Build index list
let indices: [Int] = Array(0..<arraySize)
// Shuffle and take first N
return Array(indices.shuffled().prefix(count))
}
func main() {
// Example array
let data: [Int] = [5, 12, 5, 19, 5, 33, 47, 5, 58, 61, 17, 3, 5, 74, 83, 90, 6]
let n: Int = 6 // number of unique indices to pick
// Get unique random indices
let indices: [Int] = pickUniqueIndices(arraySize: data.count, count: n)
// Print results
print("Random unique indices and their values:")
for idx in indices {
print("index \(idx) -> value \(data[idx])")
}
}
main()
/*
run:
Random unique indices and their values:
index 4 -> value 5
index 15 -> value 90
index 12 -> value 5
index 16 -> value 6
index 1 -> value 12
index 0 -> value 5
*/
