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Algorithms flashcards
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Topic 1: Algorithms
- What is an algorithm?
- A sequence of steps that solves a problem or completes a task. It must be unambiguous, finite and produce a result. A program is one implementation of an algorithm in a particular language.
- What is decomposition?
- Breaking a problem into smaller, manageable sub-problems.
- What is abstraction?
- Removing unnecessary detail to focus on what matters, e.g. an underground map keeps the connections but drops real distances.
- What is algorithmic thinking?
- Devising the sequence of steps that solves the problem.
- What do the four main flowchart symbols mean?
- Oval/rounded: start and stop. Parallelogram: input and output. Rectangle: process. Diamond: decision, with two labelled exits, Yes and No.
- What is the difference between a linear search and a binary search?
- Linear: checks each item in turn; works on data in any order; slow on large sets. Binary: compares the middle item and discards half each time; the data must be sorted; much faster.
- How does a bubble sort work?
- Repeatedly compare adjacent pairs and swap them if out of order. After each pass the largest remaining item has moved to the end. Stop when a pass makes no swaps.
- How does a merge sort work?
- Divide the list in half repeatedly until each part holds one item, then merge the parts back together in order. Faster than bubble sort on large lists but more complex.
- What is a trace table used for?
- Recording the value of each variable (one column each) as an algorithm runs line by line, to work out its output and find logic errors.