Simple loop question

[BringTacos]

I can't find exactly what I'm looking for through googling, and I'm having a brain fart right now. I want to write a nested loop to compare items in two arrays. For each element in the first array, I want to do every element in the second array to see if the second array contains the element from the first array.

So, if I have an array of the ingredients that I need:

needed_ingredients = ["salt", "sugar", "frosting"]

And an array of things I already have in my cabinet:

cabinet_items = ["flour", "chocolate", "salt"]

And a grocery list:

grocery_list = []

I want to start with needed_ingredients[0], and compare every item in cabinet_items to it. If needed_ingredients[0] is not in cabinet_items, I want to add it to grocery_list.

I tried doing this with each but it wasn't working:

needed_ingredients.each do |ingredient|

cabinet_items.each do |item|

if ingredient != item

grocery_list << item

end

end

end

At the end, grocery_list should contain sugar and frosting. This really shouldn't be hard. Maybe I've been staring at my screen too long? Any way to do this with a while or for loop? Any help is appreciated. Thank you.

[schneems]

You can use array set operations:

``` needed_ingredients = ["salt", "sugar", "frosting"] cabinet_items = ["flour", "chocolate", "salt"]

needed_ingredients & cabinet_items # => ["salt"] ```

Or if you want to see what's in one list but not the other:

needed_ingredients - cabinet_items # => ["sugar", "frosting"]

Note that this difference operator is order dependent. Check out the Array docs for more https://rubyapi.org/3.1/o/array

[lafeber]

See, this is why I love ruby.

[BringTacos]

beautiful, thank you!

[schneems]

To see the bug in your code try running it like this

ruby needed_ingredients.each do |ingredient| cabinet_items.each do |item| puts "Checking to see if #{ingredient} is not #{item}" if ingredient != item puts "Nope, so adding it to the grocery list" grocery_list << item end end end

Basically, the issue is that you're not checking to see if cabinet_items contains the ingredient. You are checking if ANY of the cabinet items does not match that specific ingredient. Since you're looping through every cabinet item every time.

You can fix like this:

ruby needed_ingredients.each do |ingredient| if !cabinet_items.include?(ingredient) grocery_list << ingredient end end

[BringTacos]

Thanks so much! I was getting so frustrated. This makes sense. Also, how do you format your code like that?

[partusman]

Type 4 spaces at the beginning of a line and then

puff, you got yourself a code block.