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SingaporeComputer Science

Algorithms and Problem Solving

5 dot points across 5 inquiry questions. Click any dot point for a focused answer with worked past exam questions where available.

What is an algorithm, and how do flowchart symbols show its steps and decisions?

Define an algorithm and represent its sequence, selection and iteration using standard flowchart symbols
A focused answer to the O-Level Computing point on algorithms and flowcharts. What an algorithm is, the standard flowchart symbols, and how to show sequence, selection and iteration in a flowchart.
7 min answer →

How do we write an algorithm in pseudocode using assignment, input, output, selection and loops?

Write algorithms in pseudocode using input, output, assignment, selection (IF) and iteration (WHILE, FOR)
A focused answer to the O-Level Computing point on pseudocode. Writing algorithms with input, output, assignment, IF selection, and WHILE and FOR loops, in clear language-independent steps.
7 min answer →

How do linear and binary search find an item, and why is binary search faster?

Describe and trace linear search and binary search, and explain why binary search needs a sorted list
A focused answer to the O-Level Computing point on searching. How linear search checks each item in turn, how binary search halves a sorted list each step, and why binary search is faster but needs sorted data.
7 min answer →

How does bubble sort put a list in order one pass at a time?

Describe and trace the bubble sort, explaining how repeated passes of comparisons and swaps sort a list
A focused answer to the O-Level Computing point on sorting. How bubble sort compares neighbouring items and swaps them, how each pass moves the largest value to the end, and tracing the algorithm by hand.
7 min answer →

How do we check an algorithm works using a trace table and well-chosen test data?

Use a trace table to follow variable values through an algorithm, and choose normal, boundary and invalid test data
A focused answer to the O-Level Computing point on tracing and testing. Building a trace table to track variables through an algorithm, and choosing normal, boundary and invalid test data to find errors.
7 min answer →