I am working on a python algorithm to find the most frequent element in the list.

def GetFrequency(a, element):
return sum([1 for x in a if x == element])def GetMajorityElement(a):n = len(a)if n == 1:return a[0]k = n // 2elemlsub = GetMajorityElement(a[:k])elemrsub = GetMajorityElement(a[k:])if elemlsub == elemrsub:return elemlsublcount = GetFrequency(a, elemlsub)rcount = GetFrequency(a, elemrsub)if lcount > k:return elemlsubelif rcount > k:return elemrsubelse:return None

I tried some test cases. Some of them are passed, but some of them fails.

For example, [1,2,1,3,4] this should return 1, buit I get None.

The implementation follows the pseudocode here: http://users.eecs.northwestern.edu/~dda902/336/hw4-sol.pdf The pseudocode finds the majority item and needs to be at least half. I only want to find the majority item.

Can I get some help? Thanks!

I wrote an iterative version instead of the recursive one you're using in case you wanted something similar.

def GetFrequency(array):majority = int(len(array)/2)result_dict = {}while array:array_item = array.pop()if result_dict.get(array_item):result_dict[array_item] += 1else:result_dict[array_item] = 1if result_dict[array_item] > majority:return array_item   return max(result_dict, key=result_dict.get)

This will iterate through the array and return the value as soon as one hits more than 50% of the total (being a majority). Otherwise it goes through the entire array and returns the value with the greatest frequency.