LESSON 388 OF 413 · PROJECTS: COMMAND-LINE TOOLS

CLI Tool: uniq v1 — Drop Adjacent Duplicates in C#

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:

public string Uniq(List<string> lines)

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 List<string> result and add the current line only if result is empty or the line differs from result[result.Count - 1]. Then join the survivors with string.Join("\n", result).

if (result.Count == 0 || lines[i] != result[result.Count - 1]) {
    result.Add(lines[i]);
}

The full solution:

class Solution {
    public string Uniq(List<string> lines) {
        List<string> result = new List<string>();
        for (int i = 0; i < lines.Count; i++) {
            if (result.Count == 0 || lines[i] != result[result.Count - 1]) {
                result.Add(lines[i]);
            }
        }
        return string.Join("\n", result);
    }
}

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CLI Tool: uniq v1 — Drop Adjacent Duplicates in C#

Uniq V1 in C#