use rand::rng; // thread‑local RNG (rand 0.9+)
use rand::seq::IndexedRandom; // needed for .choose() in rand 0.9+
// ------------------------------------------------------------
// Function: generate_number
// Purpose: Create one 3-digit integer with distinct digits,
// drawn from a shared pool of available digits.
// The first digit is never zero, so the result
// is always a true 3-digit integer.
// ------------------------------------------------------------
fn generate_number(available_digits: &mut Vec<char>, length: usize) -> i32 {
// Choose the first digit from the pool, excluding '0'
let non_zero_digits: Vec<char> = available_digits
.iter()
.cloned()
.filter(|d| *d != '0')
.collect();
let mut rng = rng(); // thread‑local RNG (rand 0.9+)
let first_digit = *non_zero_digits.choose(&mut rng).unwrap();
// Remove first digit from pool
if let Some(pos) = available_digits.iter().position(|&d| d == first_digit) {
available_digits.remove(pos);
}
// Choose the remaining digits from the updated pool
let mut remaining: Vec<char> = Vec::new();
for _ in 1..length {
let d = *available_digits.choose(&mut rng).unwrap();
remaining.push(d);
if let Some(pos) = available_digits.iter().position(|&x| x == d) {
available_digits.remove(pos);
}
}
// Build the number as a string, then convert to int
let mut digits_str = first_digit.to_string();
for d in remaining {
digits_str.push(d);
}
digits_str.parse::<i32>().unwrap()
}
// ------------------------------------------------------------
// Function: generate_three_distinct_digit_numbers
// Purpose: Produce three integers, each with distinct digits,
// and no digit repeated across all three numbers.
// All numbers are guaranteed to be 3 digits long.
// ------------------------------------------------------------
fn generate_three_distinct_digit_numbers() -> (i32, i32, i32) {
// Start with all digits 0–9 as characters
let mut digits: Vec<char> = (0..10).map(|i| char::from_digit(i, 10).unwrap()).collect();
// Generate three numbers, each 3 digits long
let n1 = generate_number(&mut digits, 3);
let n2 = generate_number(&mut digits, 3);
let n3 = generate_number(&mut digits, 3);
(n1, n2, n3)
}
// ------------------------------------------------------------
// Main execution
// ------------------------------------------------------------
fn main() {
// Run the generator 5 times
for _ in 0..5 {
let (n1, n2, n3) = generate_three_distinct_digit_numbers();
println!("({}, {}, {})", n1, n2, n3);
}
}
/*
run:
(345, 260, 879)
(527, 968, 143)
(743, 612, 580)
(247, 593, 108)
(360, 894, 125)
*/
