LESSON 389 OF 404 · PROJECTS: COMMAND-LINE TOOLS

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

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:

func trDelete(lines []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 map[rune]bool for O(1) lookup. Walk every line and append characters that are NOT in the map.

The full solution:

func trDelete(lines []string, chars string) string {
    set := make(map[rune]bool)
    for _, ch := range chars {
        set[ch] = true
    }
    result := ""
    for i := 0; i < len(lines); i++ {
        if i > 0 {
            result += "\n"
        }
        for _, ch := range lines[i] {
            if !set[ch] {
                result += string(ch)
            }
        }
    }
    return result
}

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

Tr V3 in Go