LESSON 389 OF 414 · PROJECTS: COMMAND-LINE TOOLS

CLI Tool: uniq v1 — Drop Adjacent Duplicates in Kotlin

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:

fun 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 a MutableList<String> result and add the current line only if result is empty or the line differs from result[result.size - 1]. Then join the survivors with result.joinToString("\n").

if (result.isEmpty() || lines[i] != result[result.size - 1]) {
    result.add(lines[i])
}

The full solution:

class Solution {
    fun uniq(lines: List<String>): String {
        val result = mutableListOf<String>()
        for (i in lines.indices) {
            if (result.isEmpty() || lines[i] != result[result.size - 1]) {
                result.add(lines[i])
            }
        }
        return result.joinToString("\n")
    }
}

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CLI Tool: uniq v1 — Drop Adjacent Duplicates in Kotlin

Uniq V1 in Kotlin