Task — Arrange binary

You are given a list of binary digits (0 and 1) and a positive integer, $n. Write a script to return true if you can modify the list by replacing at least $n digits with 1s so that no two consecutive digits are 1, and otherwise return false.

Examples

Example 1
Input: @digits = (1, 0, 0, 0, 1), $n = 1
Output: true
Re-arranged list: (1, 0, 1, 0, 1)

Example 2
Input: @digits = (1, 0, 0, 0, 1), $n = 2
Output: false

Analysis

There are 3 cases where we can change a 0 to a 1:

• Any sequence of 3 zeroes, 0, 0, 0 → 0, 1, 0
• A starting sequence of 0, 0 → 1, 0
• An ending sequence of 0, 0 → 0, 1

We can make this even easier by temporarily adding a zero to either end of the sequence, in which case we are simply changing 0, 0, 0 →
0, 1, 0.

And that's what I did. Most of the rest of the code is just formatting the input and output.

Try it 

#!/usr/bin/perl

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

use v5.26;    # The Weekly Challenge - 2025-01-13
use utf8;     # Week 304 - task 1 - Arrange binary
use warnings; # Peter Campbell Smith
binmode STDOUT, ':utf8';

arrange_binary ([1, 0, 0, 0, 1], 1);
arrange_binary ([1, 0, 1, 0, 1], 1);
arrange_binary ([0, 0, 1, 0, 1, 0, 0], 1);
arrange_binary ([1, 0, 0, 0, 0, 0, 0, 0, 1], 1);
arrange_binary ([0, 0, 0, 0], 1);

sub arrange_binary {
    
    my ($string, $n, $count, @ints);
    
    # initialise
    @ints = @{$_[0]};
    $n = $_[1];
    
    # join @ints as string and add 0 at each end
    $string = '0' . join('', @ints) .'0';
    
    # count possible replacements
    $count = 0;
    $count ++ while $string =~ s|000|010|;
    $string =~ s|^.(.*).$|$1|;
    
    # report result
    say qq[\nInput:  \@ints =  (] . join(', ', @ints) . qq[), \$n = $n];
    if ($count >= $n) {
        say qq[Output: true     (] . join(', ', split('', $string)) . qq[), replaced $count];
    } else {
        say qq[Output: false];
    }
}

Output

Input:  @ints =  (1, 0, 0, 0, 1), $n = 1
Output: true     (1, 0, 1, 0, 1), replaced 1

Input:  @ints =  (1, 0, 1, 0, 1), $n = 1
Output: false

Input:  @ints =  (0, 0, 1, 0, 1, 0, 0), $n = 1
Output: true     (1, 0, 1, 0, 1, 0, 1), replaced 2

Input:  @ints =  (1, 0, 0, 0, 0, 0, 0, 0, 1), $n = 1
Output: true     (1, 0, 1, 0, 1, 0, 1, 0, 1), replaced 3

Input:  @ints =  (0, 0, 0, 0), $n = 1
Output: true     (1, 0, 1, 0), replaced 2