Python Counter | Majority Element

Majority Element: A majority element in an array A[] of size n is an element that appears more than n/2 times (and hence there is at most one such element). Write a function which takes an array and emits the majority element (if it exists), otherwise prints NONE as follows: Examples:

Input : 3 3 4 2 4 4 2 4 4
Output : 4 

Input : 3 3 4 2 4 4 2 4
Output : NONE

We have existing solution for this problem please refer Majority Element link. We can solve this problem quickly in Python using Counter(iterable) function. Approach is simple,

1. Convert given list of elements into dictionary using Counter() method, having elements as keys and their frequencies as value.
2. Now traverse complete dictionary and check for element whose frequency follows the condition greater than (n/2) where n is size of list. That element will be majority element.

Python3

# Function to find majority element
from collections import Counter

def majority(arr):

    # convert array into dictionary
    freqDict = Counter(arr)

    # traverse dictionary and check majority element
    size = len(arr)
    for (key,val) in freqDict.items():
         if (val > (size/2)):
             print(key)
             return
    print('None')

# Driver program
if __name__ == "__main__":
    arr = [3,3,4,2,4,4,2,4,4] 
    majority(arr)

Output:

4