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Problem , Problem Solving, Algorithm & Flow Charts –Part 1

Presented ByManesh TCourse:101 CS

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Week 10

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Objectives of the Session Defining Problem Defining Problem Solving Need for Problem Solving Problem Solving Strategy Define-Algorithms- Rules of Algorithms Examples of Algorithms Define-Flowcharts-Rules of Flowchart Examples of Flowcharts Model Exercises Take Away Tutorials

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Problem and Problem SolvingDefinitions The state of feeling difficulty in completing any task is

called problem

The process of working through details of a problem to reach a solution. Problem solving may include mathematical or systematic operations and can be a gauge of an individual's critical thinking skills.

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Need for Problem Solving

A computer is a tool that can be used to implement a plan for solving a problem.

A computer program is a set of instructions for a computer. These instructions describe the steps that the computer must follow to implement a plan.

An algorithm is a plan for solving a problem. A person must design an algorithm. A person must translate an algorithm into a computer

program.

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ALGORITHMS AND FLOWCHARTS Algorithm

Step by step method to solve a problem is algorithm

Flow Chart Diagrammatic representation of algorithm

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Divide and conquer strategy A divide and conquer algorithm works

by recursively breaking down a problem into two or more sub-problems of the same (or related) type, until solved

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Steps in development of Algorithms1. Define Problem2. Adopt Problem solving Method3. Specify of Algorithm4. Design an Algorithm5. Check correctness of Algorithm6. Analysis of Algorithm7. Implementation of Algorithm8. Test Algorithm9. Documentation Preparation

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Qualities of a good algorithm

Inputs and outputs should be defined precisely. Each steps in algorithm should be clear and

unambiguous. Algorithm should be most effective among many different

ways to solve a problem. An algorithm shouldn't have computer code. Instead, the

algorithm should be written in such a way that, it can be used in similar programming languages.

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Algorithm Problem: How to brush your teeth Real life Example Step 1: StartStep 2: Wake upStep 3: Wash mouthStep 4: Wash brush, apply toothpasteStep 5: Brush your teethStep 6. Wash mouth and brushStep 7: Put brush back to holderStep 8: Stop

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Problem: Add two numbers

Algorithm Step 1: Start Step 2: Read A, B

Step 3: C=A+B Step 4: Print C Step 5: Stop

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AlgorithmProblem: Multiply 2 numbersStep 1: StartStep 2: Read A, BStep 3: C=A*BStep 4: Print C Step 5: Stop

Problem: Subtract 2 numbersStep 1: StartStep 2: Read A, BStep 3: C=A-BStep 4: Print C Step 5: Stop

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AlgorithmProblem: Average of 3 numbers

Step 1: Start Step 2: Read A, B, C

Step 3: Avg=(A+B+C)/3 Step 4: Print Avg Step 5: Stop

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AlgorithmProblem: Find your Age Step 1: Start Step 2: Read Byear

Step 3: Age=2015-Byear Step 4: Print Age

Step 5: Stop

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AlgorithmProblem: Area of Circle Step 1: Start Step 2: Read Radius

Step 3: Area=3.14*Radius *Radius Step 4: Print Area

Step 5: Stop

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AlgorithmProblem: Find even or odd

Step 1: Start Step 2: Read N

Step 3: Is (N%2=0) thenPrint “Even”

elsePrint “Odd”

Step 4: Stop101CS

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AlgorithmProblem: Find +ve or -ve Step 1: Start Step 2: Read Number

Step 3: Is (N>0) thenPrint “+ve number”

elsePrint “-ve Number”

Step 4: Stop

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Detailed Algorithm Step 1: Start Step 2: Read Mark

Step 3: Is (Mark>=60) thenPrint “PASS”

elsePrint “Fail”

Step 4: Stop

AlgorithmProblem: Find Pass or Fail

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The FlowchartA Flowchart is another algorithm but graphical.

shows logic solutionemphasizes individual steps and their

interconnectionsA flowchart must have a start and stopA steps in a flowchart must connect.

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Flowchart Symbols General Used Symbols

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Flow Chart: Add Two NumbersStart

Read A, B

C=A+B

Print C

Stop

AlgorithmFlowchart

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DECISION STRUCTURES The expression A>B is a logical expression it describes a condition we want to test if A>B is true (if A is greater than B) we take

the action on left print the value of A if A>B is false (if A is not greater than B) we

take the action on right print the value of B

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DECISION STRUCTURES

isA>B

Y N

Print A Print B

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Flow Chart: Find Even or OddStart

Read N

Print “Odd”

Stop

Print “Even”

IsN%2=0

NY

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Flow Chart: Find Largest of two numbersStart

Read A, B

Print “B is large”

Stop

Print “A is large”

IsA>B

NY

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Problem: Write Algorithm and Flowchart to find solution of Quadratic equation

Algorithm: Step 1: Start Step 2: Read a, b, c Step 3: d sqrt ( ) Step 4: x1 (–b + d) / (2 x a) Step 5: x2 (–b – d) / (2 x a) Step 6: Print x1, x2 Step 7: Stop

START

Reada, b, c

d sqrt(b x b – 4 x a x c)

STOP

x1 (–b + d) / (2 x a)

X2 (–b – d) / (2 x a)

4b b a c

Print X1, X2

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Assignment 1 Draw algorithm and flowchart

1. Find area of triangle (area=(1/2)*breadth*height)2. Convert Celsius to Fahrenheit temperature f = (1.8*c) + 32; 3. Find Area of Rectangle (area= b*h)4. Find Volume of cylinder(V= 3.14*R*R*Height)5. Find volume of sphere (4/3* 3.14*R*R*R)6. Find biggest of three numbers.

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Instructions to students

Study definition well Study different algorithms well Study how to draw flowchart for specific

problems. Work-out various assignment problems Approach me for any doubt clarifications

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