Codility Python Prep Roadmap.md

⏱️ Codility Python Prep Roadmap

Arrays & Prefix Sums

👉 Foundation. Almost every Codility test starts here.

• Rotate an array (cyclic rotation)
• Max slice / Maximum subarray sum (Kadane’s algorithm)
• Prefix sum queries (fast range sums)
• Distinct elements in an array

Practice:

• Codility Lesson 2 (Arrays)
• LeetCode: Maximum Subarray, Product of Array Except Self

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Counting & Hashing

👉 Using sets/dicts efficiently.

• Missing integer (first missing positive)
• Find duplicate numbers
• Count occurrences
• Two-sum with hash map

Practice:

• Codility Lesson 4 (Counting Elements)
• LeetCode: First Missing Positive, Two Sum, Contains Duplicate

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Stacks, Queues, & Leaders

👉 Classic pattern detection problems.

• Balanced parentheses / brackets
• Fish survival problem
• Stone wall (count visible rectangles)
• Dominator (majority element)
• Equi leader

Practice:

• Codility Lesson 7 (Stacks and Queues)
• LeetCode: Valid Parentheses, Majority Element

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Sorting, Greedy, & Math

👉 Fast decisions with sorting and math tricks.

• Triangle triplet (can three numbers form a triangle?)
• Max product of three numbers
• Tie ropes problem
• Count factors
• GCD / LCM (Euclidean algorithm)

Practice:

• Codility Lesson 6 (Sorting) + Lesson 10 (Prime and Composite Numbers)
• LeetCode: Greatest Common Divisor of Strings, Valid Triangle Number

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Optional Advanced Topics

👉 If time permits:

• Prefix sums + hashmaps — e.g. Genomic range query, distinct slices
• Graph BFS/DFS — e.g. frog jump, shortest path problems

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Practice Strategy

👉 How to train efficiently:

• Spend ~1 hour daily or 2–3 hours on weekends.
• Start untimed → then switch to timed sessions (30–45 min per problem).
• Always test edge cases: empty arrays, single elements, maximum input size.

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