简单的一行代码:

def most_common(lst):
    return max(set(lst), key=lst.count)

# use Decorate, Sort, Undecorate to solve the problem

def most_common(iterable):
    # Make a list with tuples: (item, index)
    # The index will be used later to break ties for most common item.
    lst = [(x, i) for i, x in enumerate(iterable)]
    lst.sort()

    # lst_final will also be a list of tuples: (count, index, item)
    # Sorting on this list will find us the most common item, and the index
    # will break ties so the one listed first wins.  Count is negative so
    # largest count will have lowest value and sort first.
    lst_final = []

    # Get an iterator for our new list...
    itr = iter(lst)

    # ...and pop the first tuple off.  Setup current state vars for loop.
    count = 1
    tup = next(itr)
    x_cur, i_cur = tup

    # Loop over sorted list of tuples, counting occurrences of item.
    for tup in itr:
        # Same item again?
        if x_cur == tup[0]:
            # Yes, same item; increment count
            count += 1
        else:
            # No, new item, so write previous current item to lst_final...
            t = (-count, i_cur, x_cur)
            lst_final.append(t)
            # ...and reset current state vars for loop.
            x_cur, i_cur = tup
            count = 1

    # Write final item after loop ends
    t = (-count, i_cur, x_cur)
    lst_final.append(t)

    lst_final.sort()
    answer = lst_final[0][2]

    return answer

print most_common(['x', 'e', 'a', 'e', 'a', 'e', 'e']) # prints 'e'
print most_common(['goose', 'duck', 'duck', 'goose']) # prints 'goose'

def most_frequent(List):

    counter = 0

    num = List[0]

 

    for i in List:

        curr_frequency = List.count(i)

        if(curr_frequency> counter):

            counter = curr_frequency

            num = i


    return num


List = [2, 1, 2, 2, 1, 3]

print(most_frequent(List))

简单的一行代码:

def most_common(lst):
    return max(set(lst), key=lst.count)

def mostCommonElement(list):
  count = {} // dict holder
  max = 0 // keep track of the count by key
  result = None // holder when count is greater than max
  for i in list:
    if i not in count:
      count[i] = 1
    else:
      count[i] += 1
    if count[i] > max:
      max = count[i]
      result = i
  return result

主要组合(“a”、“b”、“a”、“c”)->“a”

最常见的元素应该是在数组中出现超过N/2次的元素，其中N是len(数组)。下面的技术将以O(n)个时间复杂度完成，只消耗O(1)个辅助空间。

from collections import Counter

def majorityElement(arr):        
    majority_elem = Counter(arr)
    size = len(arr)
    for key, val in majority_elem.items():
        if val > size/2:
            return key
    return -1