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LESSON 626 OF 678 · PROJECTS: COMMAND-LINE TOOLS

CLI Tool: sort v1 — Ascending Alphabetical Sort

Practice

Build a tiny version of the Unix sort command. Given a list of lines, return them sorted in ascending order by character code (like LC_ALL=C sort: uppercase letters come before lowercase ones, "Zebra" before "apple", and an empty line comes first), joined by newline characters (\n). Duplicates are all kept. If the list is empty, return the empty string.

Function signature:

func sortLines(_ lines: [String]) -> String

Example:

Input: lines = ["banana", "apple", "cherry"]

Output: "apple\nbanana\ncherry"

When printed:
apple
banana
cherry

Copy the input into a fresh var array, sort it in place with sort(), then stitch it back together with joined(separator:).

The full solution:
class Solution {
    func sortLines(_ lines: [String]) -> String {
        var sortedLines = lines
        sortedLines.sort()
        return sortedLines.joined(separator: "\n")
    }
}

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