Week44.1.raku

#!/usr/bin/perl6
use v6;

use Test;


=begin pod

Task 1

Only 100, please.
You are given a string “123456789”. Write a script that would insert ”+” or ”-” in between digits so that when you evaluate, the result should be 100.

=end pod
sub MAIN(Str $number="123456789", Int :$target=100, Bool :$verbose=False, Bool :$all=False){
    # try base 8 digits of base 3
    # 0=nothing 
    # 1=+ 
    # 2=-
    my Int $bal = 1;
    my $solution="";
    my $bits=($number.chars-1); # possible permutations
    my $fail=True;

    # EVAL was too slow so let's use an accumulator and operand to avoid it.
    for 3..^(3**$bits) -> Int $i {
        # accumulator
        my Int $acc=0; 
        # initial 
        my $operand =$number.substr(0,1); # Prime with first digit
        # operator is +1 for add or -1 for subtract 
        my Int $operator = 1; # we start off adding the operand to 0 so set to +1
        
        my Int $j=$i;
        my @sum = $number.comb;
        
        # for visualisation of answer
        my Str $solution="1";
        # compose the sum
        for 1..$bits -> $index {
            my $k = $j % 3;
            if $k== 0 {
                $operand ~=@sum[$index];
                $solution~=@sum[$index];
            } elsif $k==1 {
                $acc=$acc+($operand*$operator);
                $operator = 1;
                $operand=@sum[$index];
                $solution~="+" ~ @sum[$index];
            } elsif $k==2 {
                $acc=$acc+($operand*$operator);
                $operator = -1;
                $operand=@sum[$index];
                $solution~="-" ~ @sum[$index];
            }
            
            $j=$j div 3;
        }
        # flush remaining ops
        $acc=$acc+($operand*$operator);
        # Answer is in the accumulator
        # visual answer is in $solution
        say "$i) checking $solution = "~ $acc if $verbose && $i %% 100;
        if $target == $acc {
            say "$number -> $solution = {$target} (Checked $i of {3**$bits-3} potential solutions)";
            $fail=False;
            exit unless $all;
        }
    }

    say "No solution found for $number targeting $target" if $fail;

}

Week44.2.raku

#!/usr/bin/perl6
use v6;

use Test;


=begin pod

Task 2

Make it $200
You have only $1 left at the start of the week. You have been given an opportunity to make it $200. The rule is simple with every move you can either double what you have or add another $1. Write a script to help you get $200 with the smallest number of moves.

=end pod


# A simple example shows there are about 10 operations I can see. A best solution must be less than this.
# 200 100 50 25 24 12 6 3 1 1
# if I take 10 bits in base two, a 1 is add and a 0 is double.
# Count up to 2**10 and see if == 200, if better keep solution


constant TARGET = 200;
my Int $bal = 1;
my $bestSolution="";
my $bestSolutionMoves=TARGET; # about as infinite as we need
my $bits=TARGET/10; # just a guess
for ^2**10 -> Int $i {
    my Int $j=$i;
    my Int $sum = 1;
    my Str $solution="1";
    my int $moves=0;
    for ^$bits {
        if $j +& 0x1 == 1 {
            $sum+=1;
            last if $sum>TARGET;
            $solution~="+1";
        } else {
            $sum*=2;
            last if $sum>TARGET;
            $solution~="x2";
        }
        $j=$j +> 1;
        $moves++;
        if $sum==TARGET {
            last;
        }
    }
    if $sum==TARGET and $moves < $bestSolutionMoves {
        $bestSolution=$solution ~ "=" ~ TARGET;
        $bestSolutionMoves=$moves;
    }
}

say "$bestSolution in $bestSolutionMoves moves";