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pub fn stepping_numbers(n: usize) -> Vec<usize> {
assert!(n > 0);
let mut res: Vec<_> = (0..10).collect();
let mut i = 1;
while i < res.len() {
let x = res[i];
if x >= n {
break;
}
let r = x % 10;
if r > 0 {
res.push(x * 10 + i - 1);
}
if r < 9 {
res.push(x * 10 + i + 1);
}
i += 1;
}
res[..i].to_vec()
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test() {
dbg!(stepping_numbers(100));
}
}