LESSON 400 OF 414 · PROJECTS: COMMAND-LINE TOOLS

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

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:

fun trSqueeze(lines: List<String>, chars: String): String

Example:

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

Output: "abbb\naba"

When printed:
abbb
aba

Turn chars into a HashSet with chars.toHashSet(). Walk each line tracking prev (the last char you kept); skip the current char only if it's in the set AND equals prev.

The full solution:

class Solution {
    fun trSqueeze(lines: List<String>, chars: String): String {
        val squeeze = chars.toHashSet()
        val result = mutableListOf<String>()
        for (line in lines) {
            val sb = StringBuilder()
            var prev = '\u0000'
            for (ch in line) {
                if (squeeze.contains(ch) && ch == prev) {
                    continue
                }
                sb.append(ch)
                prev = ch
            }
            result.add(sb.toString())
        }
        return result.joinToString("\n")
    }
}

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

Tr V4 in Kotlin