Count frequencies of all elements in array in Python using collections module
Last Updated :
22 Feb, 2023
Given an unsorted array of n integers which can contains n integers. Count frequency of all elements that are present in 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 many ways, refer Count frequencies of all elements in array link. In Python, we can quickly solve this problem in using Collections module.
Implementation:
Python
import collections
def CountFrequency(arr):
return collections.Counter(arr)
if __name__ = = "__main__" :
arr = [ 1 , 1 , 1 , 1 , 2 , 2 , 2 , 2 , 3 , 3 , 4 , 5 , 5 ]
freq = CountFrequency(arr)
for (key, value) in freq.items():
print (key, " -> " , value)
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Output
(1, ' -> ', 4)
(2, ' -> ', 4)
(3, ' -> ', 2)
(4, ' -> ', 1)
(5, ' -> ', 2)
The time complexity of this function is O(n), where n is the length of the input array.
The auxiliary space required by this function is O(k), where k is the number of unique elements in the input array.
Related Article : Counting the frequencies in a list using dictionary in Python
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