LESSON 391 OF 410 · PROJECTS: COMMAND-LINE TOOLS

CLI Tool: sort v3 — Numeric Sort in Java

Practice

Build the next version of the Unix sort command, this time with the -n flag baked in. Each input line is the string form of an integer that fits in 32 bits (an optional leading -, no leading +; leading zeros such as "007" are allowed). Sort the lines numerically (not lexicographically) in ascending order, and return the original strings joined by newlines (\n). Lines with the same numeric value keep their original relative order (a stable sort). The real sort -n would break such ties by comparing the text; this version does not. If the list is empty, return the empty string.

Note: lexicographic sort would put "100" before "20"; numeric sort puts 20 before 100.

Function signature:

public String sortLines(List<String> lines)

Example:

Input: lines = ["100", "20", "3", "10"]

Output: "3\n10\n20\n100"

When printed:
3
10
20
100

Pass Comparator.comparingInt(Integer::parseInt) to Collections.sort. It converts each string to int for comparison while leaving the strings themselves unchanged.

The full solution:

class Solution {
    public String sortLines(List<String> lines) {
        List<String> sortedLines = new ArrayList<>(lines);
        Collections.sort(sortedLines, Comparator.comparingInt(Integer::parseInt));
        return String.join("\n", sortedLines);
    }
}

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CLI Tool: sort v3 — Numeric Sort in Java

Sort V3 in Java