all postfixes sorted (Rust Playground: https://play.rust-lang.org/?version=stable&mode=debug&edition=2018&gist=bda017580640d3b70ea211bec7e9038b )

all_postfixes_sorted.rs

#![allow(dead_code)]

// https://play.rust-lang.org/?version=stable&mode=debug&edition=2018&gist=bda017580640d3b70ea211bec7e9038b
// Task: sorted postfixes for given list of strings
// Example: bcd -> bcd,cd,d
// Example: abc,bcd,xyz -> abc,bc,bcd,c,cd,d,xyz,yz,z

fn all_postfixes_sorted(arr: &[&str]) -> Vec<String> {
    let mut postfixes: std::collections::HashSet<String> = std::collections::HashSet::new();
    for &w in arr {
        for start_idx in 0..(w.chars().count()) {
            let slice: &str = &w[start_idx..];
            let w = String::from(slice);
            postfixes.insert(w);
        }
    }
    let mut r = postfixes.into_iter().collect::<Vec<String>>();
    r.sort();
    r
}

fn main() -> Result<(), Box<dyn std::error::Error>> {
println!("{:?}", all_postfixes_sorted(&["abc","bcd","xyz"]));
Ok(())
}

#[cfg(test)]
mod tests {
    use super::*;
    
    #[test]
    fn examples() {
        assert_eq!(all_postfixes_sorted(&["bcd"]),
        vec!["bcd","cd","d"]);
        assert_eq!(all_postfixes_sorted(&["abc","bcd","xyz"]),
        vec!["abc", "bc", "bcd", "c", "cd", "d", "xyz", "yz", "z"]);
    }
}