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Find number deleted from array
(2 answers)
Closed 5 years ago.
I have two arrays a and b. a always has one element more than b, and the arrays are mixed.
a = [1,5,7,2,4]
b = [2,4,7,1]
I want to find the extra element in a. The output should be 5.
What is the best approach in ruby? Is it good idea to use loop?
I think this is the best built-in function to get what you expect
(a - b).pop
Related
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How to invert a permutation represented by an array in-place
(3 answers)
Closed 8 months ago.
Let's say I have an array of N elements, each element representing a unique integer between 0 and N-1. Let's say I want to find the index of a given integer, I can loop through the array and return the index when I find the number. Since this is inefficient, I could make a second array, so that for first_array[10] = 55 we'd obtain second_array[55] = 10.
Now let's say that I don't want to create a second array and I want to do the switch in-place. Is there a clever way to do this, clever meaning no extra allocation, no crazy deep recursion and no searching through the whole array N times? Does this kind of operation have a name? I feel like this is a problem that must have already been solved but I can't imagine what it could be called.
Edit: This is a question about an algorithm, the answer, being an algorithm, should work the same regardless of the programming language.
if the question is about javascript, you can simply use indexOf() method.
in your case:
first_array.indexOf(55); // it will return index of **55** in first_array
This question already has answers here:
What does `:_*` (colon underscore star) do in Scala?
(4 answers)
Closed 3 years ago.
I'm wondering if it's possible to convert an array of elements to the elements themselves. For my example, I'm trying to pass individual strings into a function whose arguments are a variable number of strings. I currently have an array of strings and am trying to pass them into .toDF (which takes a variable number of strings). This is what I have:
.toDF((df.columns)
How can I convert this array into the individual elements?
You can do this with scala's splat operator (more information here):
.toDF(df.columns: _*)
This question already has answers here:
Check if elements in two arrays are same irrespective of index
(2 answers)
How do I check in Swift if two arrays contain the same elements regardless of the order in which those elements appear in?
(10 answers)
Closed 5 years ago.
I tried using sets but obviously that doesn't work. I need a function to be able to work like this:
let Array1 = [2,2,1,1]
let Array2 = [2,1,2,1]
let Array3 = [2,2,2,1]
I need my function to be able to recognize that Array1 and Array2 are equal without thinking that Array3 is the same. Any thoughts?
This question already has answers here:
Combine two Arrays into Hash
(8 answers)
Closed 6 years ago.
If i have two arrays containing about 20 separate values is it possible to combine the two into a hash? With the contents of one array acting as the keys and the other as the values?
Sure, very simple
Hash[[1,2,3,4].zip([5,6,7,8])]
=> {1=>5, 2=>6, 3=>7, 4=>8}
But it might be a problem if the arrays have not the same size.
This question already has answers here:
How do I pick randomly from an array?
(7 answers)
Closed 7 years ago.
Select a element in the array randomly WITHOUT using the Random class.
id={1,2,3,4,5}
Is there any method which belongs to the Array class that is used to randomly select an element?
You can use the sample method
[:foo, :bar].sample # => :foo, or :bar :-)
Credit this SO question/answer