LESSON 397 OF 414 · PROJECTS: COMMAND-LINE TOOLS

CLI Tool: tr v1 — Single Char Swap in Rust

Practice

Build a tiny version of the Unix tr command. Given a list of lines and two single characters fromChar and toChar, replace every occurrence of fromChar with toChar in each line, then return the lines joined by newline characters (\n).

Notes: from_char and to_char are single ASCII characters, taken literally (no escapes like \, no ranges). Upper and lower case are different characters. A line may be empty, and may not contain from_char at all.

Function signature:

fn tr(lines: Vec<String>, from_char: String, to_char: String) -> String

Example:

Input: lines = ["banana", "apple"], from_char = "a", to_char = "X"

Output: "bXnXnX\nXpple"

When printed:
bXnXnX
Xpple

Rust's str::replace swaps EVERY occurrence and returns a new String. Collect the translated lines into a Vec<String> and join them with result.join("\n").

The full solution:

impl Solution {
    fn tr(lines: Vec<String>, from_char: String, to_char: String) -> String {
        let mut result: Vec<String> = Vec::new();
        for line in &lines {
            result.push(line.replace(&from_char, &to_char));
        }
        return result.join("\n");
    }
}

STEP 1 OF 4

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CLI Tool: tr v1 — Single Char Swap in Rust

Tr V1 in Rust