LESSON 389 OF 414 · PROJECTS: COMMAND-LINE TOOLS

CLI Tool: uniq v1 — Drop Adjacent Duplicates in Scala

Practice

Build a tiny version of the Unix uniq command. Given a list of lines, drop adjacent duplicate lines (keep only the first occurrence in each consecutive run) and return the surviving lines joined by newline characters (\n).

Function signature:

def uniq(lines: List[String]): String

Example:

Input: lines = ["a", "a", "b", "c", "c", "c", "a"]

Output: "a\nb\nc\na"

When printed:
a
b
c
a

Notice that the trailing "a" survives because it is not adjacent to the first run of "a"s — only consecutive duplicates are removed.

Build an ArrayBuffer[String] result and append the current line only if result is empty or the line differs from result(result.length - 1). Then join the survivors with result.mkString("\n").

if (result.isEmpty || lines(i) != result(result.length - 1)) {
    result += lines(i)
}

The full solution:

class Solution {
    def uniq(lines: List[String]): String = {
        val result = scala.collection.mutable.ArrayBuffer[String]()
        for (i <- lines.indices) {
            if (result.isEmpty || lines(i) != result(result.length - 1)) {
                result += lines(i)
            }
        }
        return result.mkString("\n")
    }
}

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CLI Tool: uniq v1 — Drop Adjacent Duplicates in Scala

Uniq V1 in Scala