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© Janice Regan 2004 1 Problem-Solving Process 1. State the Problem (Problem Specification) 2. Analyze the problem: outline solution requirements and design an initial algorithm 3. Design and refine the algorithm to solve the problem, verify the algorithm, come up with a test plan 4. Implement the algorithm in a programming language (Java) and verify that the algorithm works 5. Maintain the program: use and modify if the problem domain changes 1. State the Problem (Problem Specification) 2. Analyze the problem: outline solution requirements and design an initial algorithm 3. Design and refine the algorithm to solve the problem, verify the algorithm, come up with a test plan 4. Implement the algorithm in a programming language (Java) and verify that the algorithm works 5. Maintain the program: use and modify if the problem domain changes

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© Janice Regan 2004 2 Problem Specification Any problem solving process consists of Input Algorithm Output Determine what information is available as input to your algorithm Determine what information is desired as output from your algorithm Any problem solving process consists of Input Algorithm Output Determine what information is available as input to your algorithm Determine what information is desired as output from your algorithm

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© Janice Regan 2004 3 Design a basic algorithm An algorithm is Any set of instructions that specifies a series of steps to correctly solve the problem There may be many different algorithms to solve a given problem Some algorithms may be more efficient than others An algorithm is Any set of instructions that specifies a series of steps to correctly solve the problem There may be many different algorithms to solve a given problem Some algorithms may be more efficient than others

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© Janice Regan 2004 4 Properties of Good Algorithms Efficiency Simplicity Precision Effectiveness Generality Levels of Abstraction Correctness Finiteness Maintainability Efficiency Simplicity Precision Effectiveness Generality Levels of Abstraction Correctness Finiteness Maintainability

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© Janice Regan 2004 5 Algorithms and Programs An algorithm is a finite set of instructions that explains the required solution step-by-step A computer can be instructed to implement many algorithms with a finite number of steps or instructions A program is a set of computer instructions that implements an algorithm An algorithm is a finite set of instructions that explains the required solution step-by-step A computer can be instructed to implement many algorithms with a finite number of steps or instructions A program is a set of computer instructions that implements an algorithm

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© Janice Regan 2004 6 Refine the algorithm Identify special cases Determine how to test to demonstrate that the algorithm works for all cases (including special cases) Verify that the algorithm is logically valid The algorithm must give the correct answer, in a finite number of reproducible steps The algorithm must terminate when the answer is determined Identify special cases Determine how to test to demonstrate that the algorithm works for all cases (including special cases) Verify that the algorithm is logically valid The algorithm must give the correct answer, in a finite number of reproducible steps The algorithm must terminate when the answer is determined

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© Janice Regan 2004 7 Implement the algorithm Translate the algorithm into a programming language. Make sure the implementation has correct syntax and semantics (it compiles) Make sure the implementation is logically correct Test and make sure the implementation works for all normal and special cases Translate the algorithm into a programming language. Make sure the implementation has correct syntax and semantics (it compiles) Make sure the implementation is logically correct Test and make sure the implementation works for all normal and special cases

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© Janice Regan 2004 8 Problem-Analysis-Coding- Execution Cycle

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© Janice Regan 2004 9 Class discussion Algorithm for solving a quadratic equation

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© Janice Regan 2004 10 Programming Methodologies Two basic approaches to programming design: Structured design (process oriented) Centered on ‘What is happening’ Code (procedures) acting on data Think in terms of breaking into tasks to be completed Object-oriented design Centered on ‘Who or what data is being affected’ Data controlling access to code Think in terms of data entities, interfaces to that data, and processes or methods applied to that data Two basic approaches to programming design: Structured design (process oriented) Centered on ‘What is happening’ Code (procedures) acting on data Think in terms of breaking into tasks to be completed Object-oriented design Centered on ‘Who or what data is being affected’ Data controlling access to code Think in terms of data entities, interfaces to that data, and processes or methods applied to that data

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© Janice Regan 2004 11 Structured Design 1. A problem is divided into smaller subproblems 2. Each subproblem is solved 3. The solutions of all subproblems are then combined to solve the problem 1. A problem is divided into smaller subproblems 2. Each subproblem is solved 3. The solutions of all subproblems are then combined to solve the problem

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© Janice Regan 2004 12 Object-Oriented Design (OOD) In OOD, a program is a collection of interacting objects An object consists of data and operations Steps in OOD: 1. Identify objects 2. Form the basis of the solution 3. Determine how these objects interact In OOD, a program is a collection of interacting objects An object consists of data and operations Steps in OOD: 1. Identify objects 2. Form the basis of the solution 3. Determine how these objects interact

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