อ.จรรยา สายนุ้ยCS.313 ภาควิ�ชาวิ�ทยาการคอมพิ�วิเตอร�

Outline1. Problem Solving

Definition Problem Problem Solving

Strategies Techniques Tools Approach

2. Programming Principle Programming

Language Programming Design Programming

Paradigms

Problem Solving DefinitionProblem

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.........................Problem Solving

The process of transforming the description of a problem into the solution of that problem by using own knowledge of the problem domain and be relying on the ability to select and use appropriate problem solving strategies, techniques and tools

Problem Domainsciences : mathematics , statistics ,

chemistry , physics, biology business : inventory , accounting education : registration , evaluation banking : ATM , loaning , report others : restaurant , transportation , hotel ,

department store

Problem Solving Strategies

Divide and Conquer Dynamic Programming Greedy Algorithms etc.

(Algorithm Design Techniques)

Problem Solving Techniques Top-down Stepwise Refinement Structured Programming Modular Design Bottom-up Approach Recursion

Problem Solving Tools Pseudo Code Flowchart Programming Languages EditorDebugger

Problem Solving ApproachSoftware Development Method or Software

Life CycleUse computers in problem solving consists of

6 steps :1. Requirement Specification2. Analysis3. Design4. Implementation5. Testing And Verification6. Documentation

Software Life Cycle1. Requirement Specification what the problem is what is needed to solve what the solution should provide any constraints and special conditions to

concern depend on familiarity with the problem

domain

Software Life Cycle2. Analysis

Input Output Constraints/Conditions Formulas

Software Life Cycle3. Design

Software Life Cycle3.1 Algorithm designAlgorithm Definition

Algorithm : a method of solution described as a sequence of steps to be performed in a specific logical order.

Software Life Cycle3.1 Algorithm designSatisfied Requirements :

Unambiguousness Generality Correctness Finiteness

Software Life Cycle3.1 Algorithm design Representation Strategy

Pseudocoding Flowcharting HIPO Chart

Software Life Cycle3.1 Algorithm design

TechniquesGreedy Method Divide and Conquer Dynamic Programming Backtracking Algorithms etc.

Software Life Cycle3.2 Data design

Input/OutputProcessTypes : constant/variables ,global/localRepresentation: number , text , etc. Structure: array, file , queue , tree , etc. Manipulation: operators , functions

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Software Life Cycle4. Implementation or Coding Programming Languages

writability readability modifiability reusability

Software Life Cycle4. Implementation or Coding Important as designing skill

programming is the art of designing efficient algorithms to meet requirements

Programming errors Debugging techniques Strategies for defensive Programming

Software Life Cycle4.Implementation or Coding Programming Errors

design errors syntax/compilation errors linker errors run-time errors warning diagnostic message

Software Life Cycle4. Implementation or Coding Debugging techniques

The ability to debug programs is another problem-solving skill that is as important as the ability to design programs

Debugging is the process of finding and correcting errors in computer programs

Software Life Cycle4. Implementation or Coding Debugging techniques

design errors quite difficult to debug , no error message

, incorrect output sometimes incorrect formula , wrong program logic ,

inappropriate data type careful review in analysis and design , use

variety of testing data

Software Life Cycle4. Implementation or Coding Debugging techniques

syntax/compilation errors Detect by compilers Something missing / undeclared var. Easy , just correct error sources

warning diagnostic message Strange but can still proceed Unreferenced var. Get rid of causes or ignore

Software Life Cycle4. Implementation or Coding Debugging techniques

linker errors Some errors prevent the linker to

create the executable moduleFunction prototypes do not match their

definitionssolution: correct prototypes

Software Life Cycle4. Implementation or Coding Debugging techniques

run-time/execution errorswhile executing , difficult to debug, abnormal

termination divide by zero , type mismatch ,index is out of

range, domain error trace/step watch some variables’ value , error

handling

Software Life Cycle4. Implementation or Coding Strategies for defensive

correction : errors debug defence : to prevent abnormal

termination /errors preparing to manage errors if (a < o) { … } using exception handler

Software Life Cycle5. Testing And Verification program verification the process of ensuring that a program

meets user requirements one of the techniques that can be used

for program verification is program testing

Software Life Cycle5. Testing And Verification program testing

the process of executing a program to demonstrate its correctness

testing methods test data testing modules : driver , stub top-down testing bottom-up testing blackbox .vs. whitebox

Software Life Cycle: Example1.Requirement Specification

เขี�ยนุ้โปรแกรมหาระยะทางระหวิ�างจด 2 จดค!อ (x1 ,y1 ) และ (x2 ,y2 )

ส#ตรค!อ

)()( 122

122 yyxx

Software Life Cycle : Example2. Analysis

Input: integer x1 , y1 , x2 และ y2Output : float & positive value

Formulas : )()( 122

122 yyxx

Software Life Cycle: Example3. Algorithm Design

Pseudocode1. Read x1 , y1 , x2 , y22. dist = sqrt((x1 - x2)2 + (y1 - y2)2)

3. Write dist4. end

Software Life Cycle: Example4. Implementation or Coding

#include <stdio.h>#include <math.h>void main(){ int x1, x2, y1, y2;

float dist; scanf(“%d %d %d %d”, &x1, &y1, &x2,

&y2); dist = sqrt((x2-x1)*(x2-x1)+(y2-y1)*(y2-

y1)); printf(“distance = %f\n”,dist);

}

Software Life Cycle: Example5. Testing And Verification verifying: compile and debug data test:3 0 0 4 output: 5.0

Software Life Cycle6. Documentation

System documentation Program documentation User documentation

Software Life Cycle6. Documentation

System documentation Context Diagram Dataflow Diagram Database Design : E-R diagram ,

Relational model , Data dictionary System modules/flowchart

Software Life Cycle6. Documentation

Program documentation Flowchart / Pseudocode Program Listing Sufficient in-program : comment ,

indentation

Software Life Cycle6. DocumentationUser documentation

Interfaces Input Examples Output Examples Error messages : causes & effect

Programming Principles Programming Languages Program Design Programming Paradigms

Programming Languages Why programming languages ?

to enable the user to enlist the help of a computer in solving problems in the domain of interest

to enable the user to bridge the gap between problem and machine domain

Program Design modular design

top-down approachbottom-up approach

stepwise refinement structured programming etc.

Programming paradigmsimperative paradigmfunctional paradigmlogic paradigmobject-oriented paradigm

Practice make perfect