Structured Problem Solving An Introduction

Structured Problem Solving An Introduction Stewart Blakeway blakews@hope.ac.uk 0151 291 3113

Aims of the presentation • to quickly list the skills to be developed on the SPS strand of the course • to officially start the course

Skills to be developed in the SPS strand of the course The most important bit • Problem Solving Skills • Programming Skills • Team Interaction Skills • Presentation Skills • Reflective Skills

Skills to be developed in the SPS strand of the module • Problem Solving Skills • Programming Skills • Team Interaction Skills • Presentation Skills • Reflective Skills

Problem Solving Skills • Analysis of Problems • Crossing a busy road • Eating a Pie • Cooking a Pie • Climbing Mount Everest ?????? • Getting PieEater to do something complicated • Writing other software to do something complicated

Problem Solving Skills • Analysis of the Structure of Solutions • Sequence • Selection • Repetition

Problem Solving Skills • Structured English • Sequence • Selection • Repetition

Programming Skills • Introduction to Java • Java Programming Constructs • Java Trainer • The PieEater • Java revisited • Object Oriented Concepts • BlueJ Integrated Development Environment • (http://www.bluej.org/about/what.html) • The PieEater again plus Close Friends • Graphics and Animation

Programming Skills • Data Structures • Selection of Appropriate Data Structures • Sorting • Searching

Team Interaction Skills • Animation Problems • Solved in Groups • Coded in Groups • Tested in Groups

Presentation Skills • Presentation of Working Animations • Demonstration of the Running Animation • Explanation of the Choice of Variables • Explanation of the Algorithmic Design • Explanation of the Data Structures Selected • Discussion of Possible Enhancements

Reflective Skills • Reflect on Team Work Activities • Reflect on the Scope of the Task • Highlight Possible Failings in the Mechanics of the Team Work Activity • Suggest Possible Improvements to Team Work Interaction

Let the course begin …..

Your First Seminar createpieeater(); pendown(); walk(); penup(); walk(); pendown(); turnright(); walk(); walk();

Let’s Loop-the-Loop No Semi Colons createpieeater(); while (test) { actions; } other actions; Sequences of Actions each Ending with a Semi Colon

Semi-colons: a working rule • Do not put them at the end of while() if () { } • Do put them at the end of other lines int a; a = 7; turnleft();

while (test) { } test • clearahead • direction != “SW” • pieinsight clearahead and pieinsight are either true or false direction != “SE” can be evaluated to either true or false

Loop Operation while (test) { actions; } other actions; Evaluate test true false

Test is True Body of Loop while (test) { • actions; } other actions; Enter Body of Loop Execute [actions;] Evaluate testAgain

Test is True while (test) { • actions; } other actions; Enter Body of Loop Execute [actions;] Evaluate testAgain

You Get the Idea

Test is False while (test) { • actions; } other actions; Jump to other actions; and Continue with the Rest of the Program

{actions;} walk(); pendown(); penup(); turnleft(); turnright(); • You add the rest

Selection • The if statement allows us to specify alternative actions depending upon a test

Selection if (test) { }else { } if (pieinsight) { eatpie(); } else { walk(); }

if inside a loop createpieeater(); randompies(20); while (clearahead) { if (pieinsight) { eatpie(); } else { walk(); } }

Counting loops - for inti; createpieeater(); for (i=0; i<5; i++) { walk(); }

In Conclusion • Problem Solving is a Skill • Riding a Bicycle • Swimming • Keeping Awake in Lectures • It Cannot be Learned Quickly • It Cannot be Learned without Practice • Every Failure is Part of the Learning Process

Lecture Exercise 1 • Draw the following grid

Trace out the following program createpieeater(); turnright(); pendown(); while (clearahead) { walk(); }

Lecture Exercise 1 Answer

Lecture Exercise 2 • Write the program for

Lecture Exercise 2 Answer createpieeater(); inti; for (i=1 ; i<=4 ; i++) { while (clearahead) { walk(); } turnright(); turnright(); }

Lecture Exercise 3 – spot the syntax error createpieeater(); inti; for (i=1 , i<=4 , i++) { while (clearahead) { walk() } turnright(); turnright();

In Conclusion • Programming Languages are Merciless • Syntax Matters • Semi Colons can be Dangerous • In Conclusion: }

Questions? • Next… • Problem Solving in your seminars • More loops • If statements • Next lecture on Algorithms • Setting of assessment next week

Structured Problem Solving An Introduction