LESSON 399 OF 414 · PROJECTS: COMMAND-LINE TOOLS

CLI Tool: tr v3 — Delete Chars (-d) in Rust

Practice

Build a version of the Unix tr -d command. Given a list of lines and a string chars, remove every character that appears in chars from each line, then return the lines joined by newline characters (\n).

Notes: chars is a non-empty ASCII string whose characters are taken literally (no ranges). Upper and lower case are different characters. A line can become empty after deleting, and then it stays as an empty line in the output.

Function signature:

fn tr_delete(lines: Vec<String>, chars: String) -> String

Example:

Input: lines = ["banana", "apple"], chars = "aeiou"

Output: "bnn\nppl"

When printed:
bnn
ppl

Put each character of chars into a HashSet<char> for O(1) lookup. Walk every line and append characters that are NOT in the set.

The full solution:

impl Solution {
    fn tr_delete(lines: Vec<String>, chars: String) -> String {
        let mut set = HashSet::new();
        for ch in chars.chars() {
            set.insert(ch);
        }
        let mut result = String::new();
        for i in 0..lines.len() {
            if i > 0 {
                result.push('\n');
            }
            for ch in lines[i].chars() {
                if !set.contains(&ch) {
                    result.push(ch);
                }
            }
        }
        return result;
    }
}

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CLI Tool: tr v3 — Delete Chars (-d) in Rust

Tr V3 in Rust