LESSON 386 OF 414 · PROJECTS: COMMAND-LINE TOOLS

CLI Tool: grep v2 — Case-Insensitive Match in Kotlin

Practice

Build the -i flag of the Unix grep command. Given a list of lines and a search pattern, return all lines that contain pattern as a substring, ignoring letter case. Return the matching lines joined by newline characters (\n).

Function signature:

fun grepCaseInsensitive(lines: List<String>, pattern: String): String

Example:

Input:
pattern = "ERR"
lines = ["Error: 1", "ok"]

Output: "Error: 1"

When printed:
Error: 1

The matching is case-insensitive but the original line (preserving its original casing) is returned. If no lines match, return the empty string "". The lines contain only ASCII characters.

Lowercase the pattern once, then for each line check line.lowercase().contains(lowerPattern). Add the ORIGINAL line on a hit.

The full solution:

class Solution {
    fun grepCaseInsensitive(lines: List<String>, pattern: String): String {
        val result = mutableListOf<String>()
        val lowerPattern = pattern.lowercase()
        for (line in lines) {
            if (line.lowercase().contains(lowerPattern)) {
                result.add(line)
            }
        }
        return result.joinToString("\n")
    }
}

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CLI Tool: grep v2 — Case-Insensitive Match in Kotlin

Grep V2 in Kotlin