use std::collections::BTreeSet;
fn rev(n: usize) -> usize {
	fn aux(acc: usize, m: usize) -> usize {
		if m == 0 {acc} else {aux(acc * 10 + m % 10, m / 10)}
	}
	aux(0, n)
}
fn f(n: usize) -> Option<BTreeSet<usize>> {
	(0..=n).rev().zip(n..).find(|&(a, b)| a == rev(a) || b == rev(b)).map(|(a, b)| 
		[a, b].iter().filter(|&&x| x == rev(x)).cloned().collect()
	)
}
fn g(n: usize) {
	println!("入力: {}\n出力: {:?}\n", n, f(n).unwrap_or_default());
}
fn main() {
	[0, 17, 100].iter().cloned().for_each(g);
}

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