readme.md

What Did I Learn?

In this challenge I learned:

1. Empty dict to count different elements

prefix = defaultdict(int)

2. Counts the frequency of the elements in the suffix (the entire list initially)

suffix = Counter(nums)

3. Add elements on the empty list and removing from the full list

for x in nums:
    prefix[x] += 1
    suffix[x] -= 1
    if suffix[x] == 0:
        del suffix[x]

4. Add the resulting one by one in the result list

result.append(len(prefix) - len(suffix))