Find number deleted from array

Question

I am quite new to ruby so bear with me, I have two arrays and we are meant to find the number which is missing.

The starting array sequence is [1,2,3,4,5,6,7,8,9] The mi

Answer 1

Use Array Difference

[1,2,3,4,5,6,7,8,9] - [3,2,4,6,7,8,1,9]
 #=> [5] 

From the docs:

ary - other_ary → new_ary

Returns a new array that is a copy of the original array, removing any items that also appear in other_ary. The order is preserved from the original array.

It compares elements using their hash and eql? methods for efficiency