Task — Disjoint sets

You are given two sets with unique integers. Write a script to figure out if they are disjoint. The two sets are disjoint if they don’t have any common members.

Examples

Example 1:
Input: @S1 = (1, 2, 5, 3, 4)
       @S2 = (4, 6, 7, 8, 9)
Output: 0 as the given two sets have common member 4.

Example 2:
Input: @S1 = (1, 3, 5, 7, 9)
       @S2 = (0, 2, 4, 6, 8)
Output: 1 as the given two sets do not have common member.

Analysis

I did not submit a solution at the time, but have written this later

Lots of ways to do this, but what I chose was:

• Make a hash of the members of @set2 using $in_set2{$_} = 1 for @set2;
• Loop $j over @set1 and output 0 if $in_set2{$j} exists
• Else output 1

Try it 

#!/usr/bin/perl

# Blog: http://ccgi.campbellsmiths.force9.co.uk/challenge

use v5.26;    # The Weekly Challenge - 2021-08-23
use utf8;     # Week 127 - task 1 - Disjoint sets
use warnings; # Peter Campbell Smith
binmode STDOUT, ':utf8';

disjoint_sets([1, 2, 5, 3, 4], [4, 6, 7, 8, 9]);
disjoint_sets([1, 2, 5, 3, 4], [10, 6, 7, 8, 9]);
disjoint_sets([1, 2, 5, 3, 4], [1, 3, 6, -1, 42]);
disjoint_sets([1, 2, 3], []);
disjoint_sets([], [1, 3, 6, -1, 42]);
disjoint_sets([], []);

sub disjoint_sets {
    
    my (@set1, @set2, %in_set2, $j);
    
    @set1 = @{$_[0]};
    @set2 = @{$_[1]};
    say qq[\nInput:  (] . join(', ', @set1) . ')' .
        qq[\n        (] . join(', ', @set2) .')';
        
    # check what's in set2  
    $in_set2{$_} = 1 for @set2;
    
    # false if its also in set1
    for $j (@set1) {
        if ($in_set2{$j}) {
            say qq[Output: 0 ($j in both sets)];
            return;
        }
    }
    
    # else true
    say qq[Output: 1];
}

Output

Input:  (1, 2, 5, 3, 4)
        (4, 6, 7, 8, 9)
Output: 0 (4 in both sets)

Input:  (1, 2, 5, 3, 4)
        (10, 6, 7, 8, 9)
Output: 1

Input:  (1, 2, 5, 3, 4)
        (1, 3, 6, -1, 42)
Output: 0 (1 in both sets)

Input:  (1, 2, 3)
        ()
Output: 1

Input:  ()
        (1, 3, 6, -1, 42)
Output: 1

Input:  ()
        ()
Output: 1