Hello, here is my solution to the Task 1 of the Week 75 of the Weekly Challenge solved in the Raku programming language.
Coins Sum
You are given a set of coins @C, assuming you have infinite amount of each coin in the set.
Write a script to find how many ways you make sum $S using the coins from the set @C.
My solution is a kind of a two-liner:
my @coins = 1, 2, 4;
my $sum = 6;
my @wallet;
@wallet.append: $_ xx ($sum div $_) for @coins;
.say for @wallet.combinations.unique(:as(*.Str)).grep({$sum == [+] $_});
The @coins array keeps the types of available coins. Then, we fill the @wallet so that we have enough real coins to make the $sum by using only a single kind of them (if that is possible at all).
For the given example, the @wallet contains the following collection:
[1 1 1 1 1 1 2 2 2 4]
The next step is to find all possible unique combinations of the coins from the wallet and take only those, whose sum is $sum.
To take only unique combinations, I am calling .unique(:as(*.Str)) which treats them as a string. This step can possibly be made more optimal.
To filter the combinations, a grep method is used, where the reduction operator is used to compute the sum: .grep({$sum == [+] $_}).
With the above input, the program prints the following combinations of coins that give the required amount:
(2 4) (1 1 4) (2 2 2) (1 1 2 2) (1 1 1 1 2) (1 1 1 1 1 1)
* * *
→ GitHub repository
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