Chapter1 Problem Solving Techniques

8/13/2019 Chapter1 Problem Solving Techniques

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Chapter 1

Problem-Solving Techniques


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Objectives

Explain the problem-solving process used to create a

computer program

Analyze a problem

Complete an IPO chart

Plan an algorithm using pseudocode and flowcharts

Desk-check an algorithm


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Problem Solving

In this lesson, you will:

Explore the thought process followed when solving

problems

Learn how to use a similar process to create acomputer solution to a problem

Called a computer program


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Solving Everyday Problems

First step in solving a problem: analyze it

E.g., problem of being hungry

Next, you plan, review, implement, evaluate, and

modify (if necessary) the solution E.g., if you are still hungry


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Solving Everyday Problems

(continued)


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Creating Computer Solutions to

Problems

Analysis tools: IPO charts, pseudocode, flowcharts

To desk-checkor hand-trace,use pencil, paper,

and sample data to walk through algorithm

A coded algorithm is called a program


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Analyzing the Problem

Analyze a problem to:

Determine the goal of solving it

Output

Determine the items needed to achieve that goal Input

Always search first for the output


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Analyzing the Problem (continued)

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IPO Charts

Use an IPO chart to organize and summarize the

results of a problem analysis

IPO:Input, Processing, and Output


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IPO Charts (continued)

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First, reduce the amount of information you need to

consider in your analysis:


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Worse than having too much information is not

having enough information to solve problem:

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Distinguish between information that is missing and

information that is implied:


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Planning the Algorithm

Algorithm: set of instructions that will transform the

problems input into its output

Record it in the Processing column of the IPO chart

Processing item: intermediate value used byalgorithm when processing input into output

Pseudocode is a tool programmers use to help

them plan an algorithm

Short English statements


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Planning the Algorithm (continued)


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Flowcharts are also used to plan an algorithm

Use standardized symbols

Symbols connected with flowlines

Oval: start/stop symbol Rectangle: process symbol

Represents tasks such as calculations

Parallelogram: input/output symbol

Represents I/O tasks


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A problem can have more than one solution:


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Hints for Writing Algorithms

This problem specification is almost identical to the one shown

earlier in Figure 2-4


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Desk-Checking the Algorithm


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(continued)


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(continued)

Valid data is data that the programmer is

expecting the user to enter

Invalid data is data that he or she is not expecting

the user to enter You should test an algorithm with invalid data

Users may make mistakes when entering data


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The Gas Mileage Problem


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Summary

Problem-solving typically involves analyzing the

problem, and then planning, reviewing, implementing,

evaluating, and modifying (if necessary) the solution

Programmers use tools (IPO charts, pseudocode,flowcharts) to help them analyze problems and

develop algorithms

During analysis, you determine the output and input

During planning, you write the steps that will transformthe input into the output


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Summary (continued)

After the analysis and planning, you desk-check

the algorithm

Follow each of the steps in algorithm by hand

Coding refers to translating the algorithm into alanguage that the computer can understand

Before writing an algorithm, consider whether you

have already solved a similar problem

Source: An Introduction to Programming with C++, Fifth Edition

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Chapter1 Problem Solving Techniques