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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

Count Nice Subarrays

Given an array of integers, count the number of contiguous subarrays that contain exactly k odd numbers.

sliding-window two-pointers subarray
+25 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

Binary Subarray with Sum

Given a binary list and a goal sum, count the number of subarrays that add up to that goal.

sliding-window two-pointers subarray
+20 pts 20m
Two Pointers & Sliding Window medium

Subarray product less than K

Count contiguous subarrays where the product of all elements is strictly less than a target K.

sliding-window two-pointers subarray
+25 pts 30m
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

Trapping Rain Water (Two Pointers)

Given an array of non-negative integers representing elevation heights, compute how much water can be trapped after rain.

two-pointers arrays water-trapping
+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
Two Pointers & Sliding Window medium

Count Nice Subarrays

Count subarrays that contain exactly k odd numbers.

sliding-window two-pointers counting
+25 pts 30m

Showing 1–10 of 10 challenges · medium · 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.