LESSON 398 OF 414 · PROJECTS: COMMAND-LINE TOOLS

CLI Tool: tr v2 — Set Translation in Rust

Practice

Build a more powerful version of the Unix tr command. Given a list of lines and two equal-length strings set1 and set2, replace every character in each line that appears in set1 at index i with set2[i]. Characters not in set1 are unchanged. Return the lines joined by newline characters (\n).

Notes: set1 and set2 have the same length, contain only ASCII characters, and set1 has no repeated character. Characters are taken literally: there are no ranges like a-z. All replacements happen at once, so set1 = "ab", set2 = "ba" swaps the two letters. Lines may be empty.

Function signature:

fn tr(lines: Vec<String>, set1: String, set2: String) -> String

Example:

Input: lines = ["banana", "cherry"], set1 = "abc", set2 = "ABC"

Output: "BAnAnA\nCherry"

When printed:
BAnAnA
Cherry

Build a HashMap<char, char> from each char of set1 to the matching char of set2. Then walk each line and translate via map.get(&ch).unwrap_or(&ch).

let mut map = HashMap::new();
for (a, b) in set1.chars().zip(set2.chars()) {
    map.insert(a, b);
}
// per char: *map.get(&ch).unwrap_or(&ch)

The full solution:

impl Solution {
    fn tr(lines: Vec<String>, set1: String, set2: String) -> String {
        let mut map = HashMap::new();
        for (a, b) in set1.chars().zip(set2.chars()) {
            map.insert(a, b);
        }
        let mut result = Vec::new();
        for line in lines {
            let mut out = String::new();
            for ch in line.chars() {
                out.push(*map.get(&ch).unwrap_or(&ch));
            }
            result.push(out);
        }
        return result.join("\n");
    }
}

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CLI Tool: tr v2 — Set Translation in Rust

Tr V2 in Rust