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I have a sorted array:
[ 'FATAL <error title="Request timed out.">', 'FATAL <error title="Request timed out.">', 'FATAL <error title="There is insufficient system memory to run this query.">' ] I would like to get something like this but it does not have to be a hash:
[ {:error => 'FATAL <error title="Request timed out.">', :count => 2}, {:error => 'FATAL <error title="There is insufficient system memory to run this query.">', :count => 1} ] 
441
The idea is to initialize another array(say count[]) with the same size N and initialize all the elements as 0. Then count the occurrences of each element of the array and update the count in the count[]. Print all the element whose count is greater than 1.
select { array. count } is a nested loop, you're doing an O(n^2) complex algorithm for something which can be done in O(n). You're right, to solve this Skizit's question we can use in O(n); but in order to find out which elements are duplicated an O(n^2) algo is the only way I can think of so far.
Ruby | Array count() operation Array#count() : count() is a Array class method which returns the number of elements in the array. It can also find the total number of a particular element in the array. Syntax: Array. count() Parameter: obj - specific element to found Return: removes all the nil values from the array.
first is a property of an array in Ruby that returns the first element of an array. If the array is empty, it returns nil. array. first accesses the first element of the array, i.e., the element at index 0 .
The following code prints what you asked for. I'll let you decide on how to actually use to generate the hash you are looking for:
# sample array a=["aa","bb","cc","bb","bb","cc"] # make the hash default to 0 so that += will work correctly b = Hash.new(0) # iterate over the array, counting duplicate entries a.each do |v| b[v] += 1 end b.each do |k, v| puts "#{k} appears #{v} times" end Note: I just noticed you said the array is already sorted. The above code does not require sorting. Using that property may produce faster code.
57
You can do this very succinctly (one line) by using inject:
a = ['FATAL <error title="Request timed out.">', 'FATAL <error title="Request timed out.">', 'FATAL <error title="There is insufficient ...">'] b = a.inject(Hash.new(0)) {|h,i| h[i] += 1; h } b.to_a.each {|error,count| puts "#{count}: #{error}" } Will produce:
1: FATAL <error title="There is insufficient ..."> 2: FATAL <error title="Request timed out."> If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
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