LESSON 384 OF 414 · PROJECTS: COMMAND-LINE TOOLS

CLI Tool: wc v4 — Mode Flag in Scala

Practice

Combine the previous three versions of wc. Given a list of lines and a mode flag, return the requested count(s) as a string. This is our own simplified interface, not the real wc flags: the real tool combines flags (such as -lw) and pads its columns with spaces.

Function signature:

def wc(lines: List[String], mode: String): String

Mode values:

"l" → line count, as a string.
"w" → word count (whitespace-separated tokens), as a string.
"c" → character count (lines only, no separating newlines), as a string.
"all" → lines + "\t" + words + "\t" + chars.

The "c" count is the one from v3 (the sum of the line lengths, no newlines). Any other mode value, for example "x" or "L" (modes are case-sensitive), gives the same result as "all". For an empty list, "l", "w" and "c" give "0" and "all" gives "0<TAB>0<TAB>0". The input is plain ASCII text.

Example:

Input: lines = ["hello", "world"], mode = "all"

Output: "2\t2\t10"

2 lines, 2 words (one per line), 10 characters total.

Compute all three counts in a single pass through lines, then branch on mode to pick the return value.

val numLines = lines.length
var numWords = 0
var numChars = 0
for (line <- lines) {
    val trimmed = line.trim
    if (trimmed.nonEmpty) { numWords += trimmed.split("\\s+").length }
    numChars += line.length
}

Use .toString to convert numbers to strings.

The full solution:

class Solution {
    def wc(lines: List[String], mode: String): String = {
        val numLines = lines.length
        var numWords = 0
        var numChars = 0
        for (line <- lines) {
            val trimmed = line.trim
            if (trimmed.nonEmpty) { numWords += trimmed.split("\\s+").length }
            numChars += line.length
        }
        if (mode == "l") { return numLines.toString }
        if (mode == "w") { return numWords.toString }
        if (mode == "c") { return numChars.toString }
        return s"$numLines\t$numWords\t$numChars"
    }
}

STEP 1 OF 11

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CLI Tool: wc v4 — Mode Flag in Scala

Wc V4 in Scala