/*
extract_digits
--------------
Scans the input string and collects only characters
that are recognized as digits by Rust's Unicode-aware
classification (`char::is_ascii_digit` or `char::is_numeric`).
Here we use `is_ascii_digit` because the example input
contains only ASCII digits, and it is slightly faster.
*/
fn extract_digits(s: &str) -> String {
// Use an iterator pipeline to filter and collect digits.
// This is efficient, expressive, and avoids manual loops.
let digits = s.chars()
.filter(|c| c.is_ascii_digit())
.collect::<String>();
digits
}
fn main() {
// Example input string
let str = "5 rust8go 9001 c c++ 17python";
// Extract digits
let digits = extract_digits(str);
// Display results
println!("Original: {}", str);
println!("Digits: {}", digits);
}
/*
run:
Original: 5 rust8go 9001 c c++ 17python
Digits: 58900117
*/
