CSC121: Problem-Solving and Algorithm Design

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.