Most Important Algorithms to Know for IB Computer Science

Selection Sort

• Selects the minimum/maximum element each pass.
• Good for understanding algorithmic comparisons.

Insertion Sort

• Builds a sorted list one element at a time.
• More efficient than bubble or selection in some cases.

Merge Sort

• Divide and conquer strategy.
• Much more efficient (O(n log n)), but requires recursion.
• Common in HL exam questions.

Recursive Algorithms

• Factorial and Fibonacci are standard examples.
• IB exams often test whether you can trace recursion with small inputs.
• For HL, recursion also links to divide-and-conquer sorting and graph traversal.

Graph Algorithms (HL Only)

Depth-First Search (DFS)

• Explores as far as possible down one branch before backtracking.

Breadth-First Search (BFS)

• Explores all neighbors first before moving deeper.

Dijkstra’s Algorithm

• Finds the shortest path between nodes in a weighted graph.
• Commonly tested in HL exams.

Data Handling Algorithms

• String manipulation: substring search, concatenation, reversal.
• Array traversals: finding max/min, counting elements, or reordering data.

These often appear as pseudocode tasks in Paper 1.

Common Mistakes Students Make

• Memorizing pseudocode without understanding logic.
• Forgetting to trace algorithms step by step in exam conditions.
• Neglecting HL graph algorithms until the last minute.
• Mixing programming syntax with IB pseudocode.

How RevisionDojo Helps

RevisionDojo provides clear algorithm breakdowns in IB pseudocode, along with worked examples and exam-style practice. Instead of memorizing code blindly, you’ll understand the logic behind each algorithm and how to adapt it for different exam questions.

FAQs

Q: Do I need to memorize the exact pseudocode?
Yes, but small syntax slips don’t matter as much as showing correct logic. RevisionDojo’s pseudocode guides help you master IB-style formatting.

Q: Are HL algorithms much harder than SL ones?
HL adds recursion and graph algorithms, which require more abstraction. But with step-by-step practice, they become very manageable.

Q: Which algorithm comes up most often in exams?
Sorting and searching algorithms appear regularly. Binary search, bubble sort, and merge sort are the most common.

Conclusion

The most important algorithms for IB Computer Science include searching, sorting, recursion, and (for HL) graph algorithms. Mastering these will give you a strong foundation for both Paper 1 and your IA. Remember — it’s not just about memorization but about understanding and applying algorithms under exam conditions.

With RevisionDojo’s algorithm guides, you’ll learn to approach every problem with clarity and confidence, setting yourself up for a 7.

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