Python Coding
Challenges

Lists & Arrays easy

Two Sum

Return indices (i, j) with i < j such that nums[i] + nums[j] == target.

dict complement

+18 pts 16m

Dicts & Sets easy

Word frequency

Return a dict mapping each word to its count in the sentence.

dict counter

+10 pts 10m

Dicts & Sets medium

Group anagrams

Group words that are anagrams of each other.

dict sorting strings

+22 pts 20m

Dicts & Sets easy

First non-repeating character

Find the index of the first character that appears only once.

dict strings counter

+12 pts 12m

Dicts & Sets easy

Most frequent element

Return the element that appears most often in a list.

counter dict

+8 pts 8m

Dicts & Sets medium

Subarray sum equals K

Count the number of contiguous subarrays whose sum equals k.

prefix-sum dict arrays

+28 pts 25m

Data Structures & Algorithms hard

LRU cache decorator

Implement @lru_cache(maxsize=N) for unary functions using OrderedDict.

decorators caching OrderedDict

+50 pts 40m