INTRODUCTION TO PROBLEM
SOLVING
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Introduction
• Algorithm
– A sequence of precise instructions that
leads to a solution
• Program
– An algorithm expressed in a language the
computer can understand
2

Introduction (cont.)
Example:
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Introduction (cont.)
• Programming is a creative process
– No complete set of rules for creating a program
4

Programming Process
• Program Design Process
– Problem Solving Phase
• Result is an algorithm that solves the problem
– Implementation Phase
• Result is the algorithm translated into a programming
language
• Be certain the task is completely specified
– What is the input?
– What information is in the output?
– How is the output organized?
5

Programming Process (cont.)
• Develop the algorithm before implementation
– Experience shows this saves time in getting your
program to run.
– Test the algorithm for correctness
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Programming Process (cont.)
Implementation Phase
• Translate the algorithm into a programming
language
• Compile the source code
– Locates errors in using the programming language
• Run the program on sample data
– Verify correctness of results
• Results may require modification of
the algorithm and program
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Programming Process (cont.)
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Programming Process (cont.)
Example:
• STEP 1: PROBLEM ANALYSIS
– Purpose:
• To describe in details a solution to a problem by providing the
needed information for the problem.
– How?
• First, understand & study the problem.
– Identify:
• The input to the problem.
• The required output.
• The relevant process. For example, scientific formula or
appropriate theories if any.
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Programming Process (cont.)
Problem : Write a program that get 3 numbers
as input from user. Find the average and
display the numbers and the average.
Problem Analysis:
Input: 3 numbers.
Process: 1. Add the numbers
2. Divide the total with 3
Output: The 3 numbers and average
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Programming Process (cont.)
INPUT PROCESS OUTPUT
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Programming Process - Representation
Method
• STEP 2: PROGRAM DESIGN
• Definition: It defines the framework or the flow or the
problem solution
1. Algorithm
– Algorithm is a sequence of instructions to solve a
problem written in human language and problem
can be solved if follow the correct procedure
– A programmer writes the solution in the form of an
algorithm before coding it into computer language.
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Programming Process - Representation
Method (cont.)
Example of algorithm to calculate the average
of 3 numbers:
1. Set Total=0, average=0;
2. Input 3 numbers
3. Total up the 3 numbers
Total= total of 3 numbers
4. Calculate average
average=Total/3
5. Display 3 numbers and the average
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Programming Process - Representation
Method (cont.)
2. Flowchart
• A graphical representation of data,
information and process or an orderly step-
by-step solution to a problem.
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Programming Process - Representation
Method (cont.)
Start
Example:
Input a, b, c
Total = a + b + c
average = Total / 3
Display a, b, c
Display average
End
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Programming Process - Representation
Method (cont.)
3. Pseudocode
• Steps in problem solving written in certain of
programming code and certain in human
language.
• For example, some part use C++ language
code and some part use English-like phrases.
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Programming Process - Representation
Method (cont.)
START
INPUT a, b, c
Total = a + b + c
average = Total / 3
OUTPUT a, b, c
OUTPUT average
END
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Programming Process - Representation
Method (cont.)
STEPS 3: PROGRAM CODING
• Definition: Write a solution into a specific
programming language such as C, C++, COBOL
and etc.
• Solution: Instructions before it is coded into
programming language.
• Purpose: To produce a program to develop a
system.
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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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Solving Everyday Problems (continued)
21

Creating Computer Solutions to
Problems
• Analysis tools: IPO charts, pseudocode,
flowcharts
• To desk-check or hand-trace, use pencil,
paper, and sample data to walk through
algorithm
• A coded algorithm is called a program
22

Creating Computer Solutions to
Problems (continued)
23

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)
25

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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IPO Charts (continued)
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Analyzing the Problem (continued)
• First, reduce the amount of information you
need to consider in your analysis:
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Analyzing the Problem (continued)
• Worse than having too much information is
not having enough information to solve
problem:
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Analyzing the Problem (continued)
• 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 problem’s input into its output
– Record it in the Processing column of the IPO
chart
• Processing item: intermediate value used by
algorithm 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)
33

Planning the Algorithm (continued)
• 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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Planning the Algorithm (continued)
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Planning the Algorithm (continued)
• A problem can have more than one solution:
36

Hints for Writing Algorithms
This problem specification is almost identical to the one shown
earlier in Figure 2-4
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Hints for Writing Algorithms
(continued)
You may use a portion of a previous solution to solve current problem
38

Desk-Checking the Algorithm
39

Desk-Checking the Algorithm
(continued)
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Desk-Checking the Algorithm
(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
42

The Gas Mileage Problem (continued)
• After planning the algorithm, you desk-check
it:
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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 transform
the 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 a language that the computer can
understand
• Before writing an algorithm, consider
Source: An Introductionhave already solved a similar
whether you to Programming with C++, Fifth Edition
problem
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