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# Counting frequencies of all elements in an array in Python using the collections module

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An unsorted array of n integers is given, which can contain n integers. Count the frequency of all elements present in the array.
Examples:

` Input: arr [] = [1, 1, 1, 1, 2, 2, 2, 2, 3, 3, 4, 5, 5] Output: 1 -" 4 2 -" 4 3 -" 2 4 -" 1 5 -" 2 `

This problem can be solved in different ways, see Counting the frequencies of all elements in the array . In Python, we can quickly fix this problem with the Collections module .

` `

` # Function to count the frequency of each element import collections   # returns the dictionary data structure # keys are array elements and values ​​are their # corresponding frequencies {1: 4, 2: 4, 3: 2, # 5: 2, 4: 1} def CountFrequency (arr): return collections.Counter (arr)     # Driver function if __ name__ = = "__ main__" :   arr = [ 1 , 1 , 1 , 1 , 2 , 2 , 2 , 2 , 3 , 3 , 4 , 5 , 5 ] freq = CountFrequency (arr)      # repeat a dictionary named freq for printing # number of each item for key, value in freq.iteritems (): print key, " -" " , value `

Output:

` 1 -" 4 2 -" 4 3 -" 2 4 -" 1 5 -" 2 `

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