CSC121: Problem-Solving and Algorithm Design

Study Notes

What is a Problem?

A problem is a state of difficulty that needs to be resolved, a question raised for consideration or solution, or a difficulty that requires a decision on what to do.
A problem can be caused by different reasons and can usually be solved in a number of different ways.
Types of problems:
- Knowledge-lean problems: can be solved by using instructions and general problem-solving skills (e.g., finding a parking space, shampooing hair).
- Knowledge-rich problems: require specific knowledge or skills to solve the problem (e.g., calculus, computer programming).

Examples of Problems

Simple problems: making a cup of tea, cooking a pot of rice, logging into an email account.
Complex problems: traffic light control, public transport schedule, online transaction payment.

What is Problem-Solving?

Problem-solving is the process of finding a solution to a problem, making the problem go away.
It involves making a plan to solve the problem, executing the plan, and evaluating the solution.
Examples of problem-solving:
- Making a cup of tea: 1) put a teabag into a cup, 2) pour boiled water, 3) add sugar and milk, 4) stir.
- Logging into a Google email account: 1) go to mail.google.com, 2) enter email ID, 3) enter password, 4) enter or click on login button.

Program Development Life Cycle

The program development life cycle consists of five stages:
- Problem analysis: understanding the problem and identifying the requirements.
- Algorithm design: designing a solution to the problem.
- Algorithm implementation: coding the solution.
- Program testing and debugging: testing and fixing errors in the program.
- Program maintenance and documentation: making necessary changes to the program and documenting the changes.

Problem Analysis

Problem analysis involves understanding the problem, identifying the requirements, and designing a solution.
It involves breaking down the problem into smaller parts, identifying the inputs, processes, and outputs.
Examples of problem analysis:
- Example 1: Compute the sum of 3 numbers.
- Example 2: Calculate and display the average mark of three students.

Algorithm and Algorithm Presentation

An algorithm is a step-by-step procedure for solving a problem.
Algorithm presentation can be in the form of pseudocode or flowcharts.
Pseudocode is a tool used to plan an algorithm, using English-like phrases to describe the processing process.
Characteristics of a good algorithm:
- Easy to understand, precise, and clear.
- Gives the correct solution in all cases.
- Eventually ends.

Pseudocode

Pseudocode is a step-by-step problem-solving procedure.
It is used to plan an algorithm, making it easier to understand and debug.
Criteria of a good pseudocode:
- Easy to understand, precise, and clear.
- Gives the correct solution in all cases.
- Eventually ends.

Flowchart

A flowchart is a graphical representation of an algorithm.
It uses symbols and arrows to represent the flow of control.
Types of flowchart structures:
- Repetition/loop structure: used to execute statements repeatedly while a condition remains true.

Algorithm-Flowchart Example

Example 1: Compute the sum of 3 numbers.
Example 2: Calculate and display the average mark of three students.

Algorithm-Pseudocode Example

Example 1: Compute the sum of 3 numbers.
Example 2: Calculate and display the average mark of three students.

Description

This quiz covers the basics of problem-solving, algorithm design, and program development life cycle in computer science. Topics include problem analysis, algorithm design, implementation, testing, and maintenance.