LESSON 373 OF 413 · PROJECTS: COMMAND-LINE TOOLS

CLI Tool: cat v2 — Number Lines (-n) in C#

Practice

Now build the -n flag of the cat tool, as a new function. It prints every line preceded by its 1-based line number, right-aligned in 6 columns, then a tab character, then the line text. Blank lines are numbered too, and an empty list gives an empty string.

Function signature:

public string NumberedCat(List<string> lines)

Format per line: the line number right-aligned in a field 6 characters wide (padded with spaces on the left), then a literal tab (\t), then the original line.

Example:

Input: lines = ["hello", "world", "foo"]

Output:
"     1\thello\n     2\tworld\n     3\tfoo"

When printed:
     1	hello
     2	world
     3	foo

Use a StringBuilder to accumulate the output. Iterate by index, append a "\n" before every line except the first, then append the formatted line.

Use String.Format("{0,6}\t{1}", i + 1, lines[i]) to format each entry. The ,6 in {0,6} right-aligns the number in a field 6 characters wide.

The full solution:

class Solution {
    public string NumberedCat(List<string> lines) {
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < lines.Count; i++) {
            if (i > 0) {
                sb.Append("\n");
            }
            sb.Append(String.Format("{0,6}\t{1}", i + 1, lines[i]));
        }
        return sb.ToString();
    }
}

STEP 1 OF 6

Guided

Ctrl + Enter to check

CLI Tool: cat v2 — Number Lines (-n) in C#

Cat V2 in C#