LESSON 390 OF 404 · PROJECTS: COMMAND-LINE TOOLS

CLI Tool: tr v4 — Squeeze Repeats (-s) in Go

Practice

Build a version of the Unix tr -s command. Given a list of lines and a string chars, collapse consecutive runs of any character that appears in chars to a single occurrence. Other characters are unchanged. Return the lines joined by newline characters (\n).

Notes: chars is a non-empty ASCII string whose characters are taken literally (no ranges). Only runs of the same character from chars are collapsed; all other characters, and runs of characters not in chars, stay as they are. Upper and lower case are different characters. Lines may be empty.

Function signature:

func trSqueeze(lines []string, chars string) string

Example:

Input: lines = ["aaabbb", "abaa"], chars = "a"

Output: "abbb\naba"

When printed:
abbb
aba

Build a map[byte]bool acting as a set of the squeeze characters. Walk each line tracking prev (the last byte you kept); skip the current byte only if it's in the set AND equals prev.

The full solution:

func trSqueeze(lines []string, chars string) string {
    squeeze := make(map[byte]bool)
    for i := 0; i < len(chars); i++ {
        squeeze[chars[i]] = true
    }
    result := []string{}
    for i := 0; i < len(lines); i++ {
        var sb strings.Builder
        var prev byte = 0
        for j := 0; j < len(lines[i]); j++ {
            ch := lines[i][j]
            if squeeze[ch] && ch == prev {
                continue
            }
            sb.WriteByte(ch)
            prev = ch
        }
        result = append(result, sb.String())
    }
    return strings.Join(result, "\n")
}

STEP 1 OF 15

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CLI Tool: tr v4 — Squeeze Repeats (-s) in Go

Tr V4 in Go