use rand::{rng, random_range};
/*
Select N unique random indices from an existing vector in Rust.
Return the indices and print both the index and the corresponding value.
Approach:
- Build a vector of indices: 0, 1, 2, ..., size-1.
- Shuffle the indices using Fisher–Yates.
- Take the first N shuffled indices — guaranteed unique.
- Return those indices to the caller.
*/
/** Shuffle an index vector using Fisher–Yates */
fn shuffle_indices(indices: &mut Vec<usize>) {
let mut _rng = rng(); // thread-local RNG (rand 0.9+)
// Fisher–Yates shuffle
for i in (1..indices.len()).rev() {
// random_range returns a usize when the range is usize
let j: usize = random_range(0..=i);
indices.swap(i, j);
}
}
/** Return N unique random indices */
fn pick_unique_indices(array_size: usize, count: usize) -> Vec<usize> {
if count > array_size {
panic!("Cannot pick more unique indices than array size.");
}
// Build index list
let mut indices: Vec<usize> = (0..array_size).collect();
// Shuffle them
shuffle_indices(&mut indices);
// Return first N indices
indices[..count].to_vec()
}
fn main() {
// Example vector
let data: Vec<i32> = vec![5, 12, 5, 19, 5, 33, 47, 5, 58, 61, 17, 3, 5, 74, 83, 90, 6];
let n: usize = 6; // number of unique indices to pick
// Get unique random indices
let indices: Vec<usize> = pick_unique_indices(data.len(), n);
// Print results
println!("Random unique indices and their values:");
for idx in indices {
println!("index {} -> value {}", idx, data[idx]);
}
}
/*
run:
Random unique indices and their values:
index 15 -> value 90
index 13 -> value 74
index 4 -> value 5
index 1 -> value 12
index 14 -> value 83
index 10 -> value 17
*/
