top2Frequent.py

top2Frequent.py

#import collections

def top2Frequent(nums):
    """
    :type nums: List[int]
    :type k: int
    :rtype: List[int]
    """
    if len(nums) < 2:
        return []
    counter = {}
    for num in nums:
        if num in counter:
            counter[num] = counter[num] + 1
        else:
            counter[num] = 1

    # The line below creates an iterator that will generate the
    # sequence [(4, 3), (3, 2), (5, 1), (1, 1)], i.e.
    # count the occurrence for each value.
    # In particular, sorted() with key=lambda kv: kv[1] will turn
    # a dictionary into a list of tuples, sorted by the second item
    # of each tuple

    sorted_by_value = reversed(sorted(counter.items(), key=lambda kv: kv[1]))

    top_vals = [item[0] for item in sorted_by_value][:2]

    return top_vals             
            
"""            
    bucket = collections.defaultdict(list)
    for key in freq:
        f = freq[key]
        bucket[f].append(key)
    res = []
    count = len(nums)  # the upper limit for res
    while len(res) < 2:
        if bucket[count]:
            res += bucket[count]
        count -= 1
    return res
"""

nums = [1, 4, 3, 4, 5, 3, 4]  # [4,3]
solution = top2Frequent(nums)
print(solution) # [4,3]

Without using the built-in collections module, the above code will work: