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I have an array like [1,1,1,2,4,6,3,3] and I would like to get the list of repeated elements, in this case [1,3]. I wrote this:
my_array.select{|obj|my_array.count(obj)>1}.uniq
But it is tragically inefficient (o(n²)). Do you have a better idea? If possible concise.
Thanks
321
Duplicate elements can be found using two loops. The outer loop will iterate through the array from 0 to length of the array. The outer loop will select an element. The inner loop will be used to compare the selected element with the rest of the elements of the array.
With the uniq method you can remove ALL the duplicate elements from an array. Let's see how it works! Where the number 1 is duplicated. Calling uniq on this array removes the extra ones & returns a NEW array with unique numbers.
We can remove duplicate element in an array by 2 ways: using temporary array or using separate index. To remove the duplicate element from array, the array must be in sorted order. If array is not sorted, you can sort it by calling Arrays. sort(arr) method.
The each() is an inbuilt method in Ruby iterates over every element in the range. Parameters: The function accepts a block which specifies the way in which the elements are iterated. Return Value: It returns every elements in the range.
Inspired by Ilya Haykinson's answer:
def repeated(array)
counts = Hash.new(0)
array.each{|val|counts[val]+=1}
counts.reject{|val,count|count==1}.keys
end
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