use std::f64;
fn is_prime(n: i32) -> bool {
if n < 2 {
return false;
}
if n % 2 == 0 {
return n == 2;
}
let limit = (n as f64).sqrt() as i32;
let mut i = 3;
while i <= limit {
if n % i == 0 {
return false;
}
i += 2;
}
true
}
fn has_unique_digits(mut n: i32) -> bool {
let mut seen = [false; 10];
while n > 0 {
let d = (n % 10) as usize;
if seen[d] {
return false;
}
seen[d] = true;
n /= 10;
}
true
}
fn main() {
for num in 1000..=9999 {
if is_prime(num) && has_unique_digits(num) {
println!("First 4-digit prime with all unique digits: {}", num);
return; // stop after finding the first one
}
}
println!("No such number found.");
}
/*
run:
First 4-digit prime with all unique digits: 1039
*/
