/*
Select N unique random indices from an existing array in TypeScript.
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 Fisher–Yates (efficient and predictable).
- Take the first N shuffled indices — guaranteed unique.
- Return those indices to the caller.
*/
/** Shuffle an array of indices using Fisher–Yates */
function shuffleIndices(indices: number[]): void {
for (let i: number = indices.length - 1; i > 0; i--) {
const j: number = Math.floor(Math.random() * (i + 1)); // random index in [0..i]
const temp: number = indices[i];
indices[i] = indices[j];
indices[j] = temp;
}
}
/** Return N unique random indices */
function pickUniqueIndices(arraySize: number, count: number): number[] {
if (count > arraySize) {
throw new Error("Cannot pick more unique indices than array size.");
}
// Build index list
const indices: number[] = Array.from({ length: arraySize }, (_, i) => i);
// Shuffle them
shuffleIndices(indices);
// Return first N indices
return indices.slice(0, count);
}
// Example array
const data: number[] = [5, 12, 5, 19, 5, 33, 47, 5, 58, 61, 17, 3, 5, 74, 83, 90, 6];
const N: number = 6; // number of unique indices to pick
// Get unique random indices
const indices: number[] = pickUniqueIndices(data.length, N);
// Print results
console.log("Random unique indices and their values:");
for (const idx of indices) {
console.log(`index ${idx} -> value ${data[idx]}`);
}
/*
run:
Random unique indices and their values:
index 7 -> value 5
index 11 -> value 3
index 2 -> value 5
index 9 -> value 61
index 15 -> value 90
index 14 -> value 83
*/
