As a result of doing a programming quiz at work, two people got the same answer, so make a note

What is SET INTERSECTION?

A programming quiz like FizzBuzz. This time we will challenge the problems listed in CodeEval.

CodeEval - https://www.codeeval.com/browse/30/

Problem (free translation)

The input value is a list of two sorted numbers (in ascending order). The list is separated by ;, and the numbers in the list are separated by ,. Outputs duplicate numbers in two types of lists, separated by ,.

`Input value sample`


1,2,3,4;4,5,6

20,21,22;45,46,47

7,8,9;8,9,10,11,12

`Output value sample`


4

(No output)

8,9

Since I did it in Java this time, it is assumed that one line of input value sample is entered in args [0].

`Such an image`


java SetIntersection "1,2,3,4;4,5,6"

Answer: I wrote it in one line (playful)

It has become a one-liner in many ways. (No modularization or exception handling is considered)

import java.util.Arrays;
import java.util.stream.Collectors;

public class SetIntersection {
  public static void main(String[] args) {

    System.out.println(String.join(",",
        Arrays.stream(args[0].split(";")[0].split(","))
            .filter(leftString -> Arrays.stream(args[0].split(";")[1].split(",")).anyMatch(leftString::equals))
            .collect(Collectors.toList())));

  }
}

Answer: Disassembled for readability

Use filter to narrow down and list only those that meet the conditions of ʻanyMatch. The rest is to output with String.join` separated by commas.

import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.Stream;

public class SetIntersection {

  private static final String SEPARATOR_LIST = ";";
  private static final String SEPARATOR_NUMBER = ",";

  public static void main(String[] args) {

    Stream<String> leftSide = Arrays.stream(args[0].split(SEPARATOR_LIST)[0].split(SEPARATOR_NUMBER));
    List<String> rightSide = Arrays.asList(args[0].split(SEPARATOR_LIST)[1].split(SEPARATOR_NUMBER));

    System.out.println(String.join(SEPARATOR_NUMBER,
                                   leftSide.filter(leftString -> rightSide.stream().anyMatch(leftString::equals))
                                           .collect(Collectors.toList())));

  }
}

The answer at work was divided into the method using for and ʻif and the method using stream`. Needless to say, the former has a faster execution speed.

[Java] Write the programming quiz SET INTERSECTION in one line with StreamAPI