Jeroo Chapter 3 Problem Solving and Algorithms

Problem Solving and Algorithms  The story of Aunt Kay  A computer is a tool used to solve problems  A computer program is a set of instructions.  An algorithm is a plan for solving a problem.  A person must design an algorithm.  A person must translate an algorithm into a computer program.

An Algorithm Development Process  The development of the algorithm is the key step.  Step 1: Obtain a description of the problem  Step 2: Analyze the problem  Step 3: Develop a high-level algorithm  Step 4: Refine algorithm by adding detail  Step 5: Review the algorithm

Obtain a Description of the Problem  The “client” is responsible for creating a description of the problem for the “developer”  Common Problem Description Defects:  The description relies on unstated assumptions  The description is ambiguous  The description is incomplete  The description has internal contradictions  Part of developer’s responsibility is to identify defects in the description and work to fix them

Analyze the problem  Determine starting and ending points for solving the problem.  Starting Point:  What data are available?  Where is the data?  What formulas pertain to the problem?  What rules exist for working with the data?  What relationships exist among the data values?

Analyze the problem  When determining ending point, describe the characteristics of a solution.  How will we know when we are done?  What new facts will we have?  What items will have changed?  What changes will have been made to those items?  What things will no longer exist?

Develop a high level algorithm  Add detail later….  Problem: I need to send a birthday card to my brother, Mark.  Analysis: I don’t have a card. I prefer to buy a card rather than make one.  High Level Algorithm:  Go to store that sells greeting cards  Select a card  Purchase a card  Mail the card

Develop a high level algorithm  How much detail do we add?  Who is going to implement the algorithm and how much they already know.  If the goal is to develop an algorithm that leads to a computer program, consider:  Capabilities of the computer  Provide enough detail so someone else can write a program  Better to have more detail if you are in doubt.

Review the algorithm  Will it solve original problem?  Once satisfied:  Specific or general problem?  Ex. Algorithm that computes the area of a circle with a radius of 5.2 meters = specific  Algorithm that computes the area of any circle = general  Can the algorithm be simplified?  Is solution similar to the solution of another problem?

5 Step Algorithm Creation Process  Step 1: Obtain a description of the problem  Step 2: Analyze the problem  Step 3: Develop a high-level algorithm  Step 4: Refine algorithm by adding detail  Step 5: Review the algorithm