Practice Arena

Python Coding Challenges

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925 challenges 556 easy 323 medium 46 hard
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Two Pointers & Sliding Window medium

Sort Colors (Dutch National Flag)

Implement the Dutch National Flag algorithm to sort an array of 0, 1, 2 in one pass.

in-place two-pointers sorting
+20 pts 25m
Two Pointers & Sliding Window medium

Reverse Pairs Count

Implement a function to count reverse pairs in an array efficiently.

arrays counting sorting
+20 pts 25m
Two Pointers & Sliding Window medium

Three Sum

Given an array of integers, return all unique triplets that sum to zero.

sorting two-pointer unique-triplets
+25 pts 25m
Two Pointers & Sliding Window medium

Closest Three Sum

Given an array of integers and a target, return the sum of three numbers that is closest to the target.

sorting two-pointers array
+20 pts 20m
Two Pointers & Sliding Window easy

Squares of Sorted Array

Implement a function that returns a sorted list of squares for a given non-decreasing integer array.

two-pointers sorting array
+10 pts 15m
Two Pointers & Sliding Window medium

Boats to Save People – Two Pointer

Implement a function that returns the minimum number of boats needed to rescue everyone, given a weight limit and each boat carrying at most two people.

two-pointers sorting greedy
+25 pts 30m
Two Pointers & Sliding Window medium

Sliding Window Median

Given a list of integers and a positive window size k, return the median of each sliding window of length k.

sliding-window median sorting
+25 pts 25m
Two Pointers & Sliding Window medium

Four Sum

Find all unique quadruplets in an array that sum to a given target.

two-pointers sorting set
+30 pts 25m

Showing 1–8 of 8 challenges · Two Pointers & Sliding Window

Two Pointers & Sliding Window — Python coding challenges

What you will find here

This page lists two pointers & sliding window challenges — real Python problems you solve in the browser IDE with instant test feedback. Each challenge includes a clear brief, starter code, and automated checks.

Challenges vs tutorials and quizzes

Challenges test what you can build under constraints. For guided teaching, use our Python tutorials. For quick checks, try quizzes or copy snippets from code samples.