LESSON 395 OF 410 · PROJECTS: COMMAND-LINE TOOLS

CLI Tool: tr v3 — Delete Chars (-d) in Java

Practice

Build a version of the Unix tr -d command. Given a list of lines and a string chars, remove every character that appears in chars from each line, then return the lines joined by newline characters (\n).

Notes: chars is a non-empty ASCII string whose characters are taken literally (no ranges). Upper and lower case are different characters. A line can become empty after deleting, and then it stays as an empty line in the output.

Function signature:

public String trDelete(List<String> lines, String chars)

Example:

Input: lines = ["banana", "apple"], chars = "aeiou"

Output: "bnn\nppl"

When printed:
bnn
ppl

Put each character of chars into a HashSet<Character> for O(1) lookup. Walk every line and append characters that are NOT in the set.

The full solution:

class Solution {
    public String trDelete(List<String> lines, String chars) {
        Set<Character> set = new HashSet<>();
        for (int i = 0; i < chars.length(); i++) {
            set.add(chars.charAt(i));
        }
        List<String> result = new ArrayList<>();
        for (String line : lines) {
            StringBuilder sb = new StringBuilder();
            for (int j = 0; j < line.length(); j++) {
                char ch = line.charAt(j);
                if (!set.contains(ch)) {
                    sb.append(ch);
                }
            }
            result.add(sb.toString());
        }
        return String.join("\n", result);
    }
}

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CLI Tool: tr v3 — Delete Chars (-d) in Java

Tr V3 in Java