UNIT I
ALGORITHMIC PROBLEM SOLVING
Algorithms, building blocks of algorithms (statements, state, control flow, functions),
notation (pseudo code, flow chart, programming language), algorithmic problem
solving, simple strategies for developing algorithms (iteration, recursion). Illustrative
problems: find minimum in a list, insert a card in a list of sorted cards, Guess an
integer number in a range, Towers of Hanoi.
1.PROBLEM SOLVING
Problem solving is the systematic approach to define the problem and creating
number of solutions.
The problem solving process starts with the problem specifications and ends with a
Correct program.
1.1 PROBLEM SOLVING TECHNIQUES
Problem solving technique is a set of techniques that helps in providing logic for solving
a problem.
Problem Solving Techniques:
Problem solving can be expressed in the form of
1. Algorithms.
2. Flowcharts.
3. Pseudo codes.
4. programs
1.2.ALGORITHM
It is defined as a sequence of instructions that describe a method for solving a
problem. In other words it is a step by step procedure for solving a problem.
Properties of Algorithms
Should be written in simple English
Each and every instruction should be precise and unambiguous.
Instructions in an algorithm should not be repeated infinitely.
Algorithm should conclude after a finite number of steps.
Should have an end point
Derived results should be obtained only after the algorithm terminates.
Qualities of a good algorithm
The following are the primary factors that are often used to judge the quality of the
algorithms.
Time – To execute a program, the computer system takes some amount of time. The
lesser is the time required, the better is the algorithm.
Memory – To execute a program, computer system takes some amount of memory
space. The lesser is the memory required, the better is the algorithm.
Accuracy – Multiple algorithms may provide suitable or correct solutions to a given
problem, some of these may provide more accurate results than others, and such
algorithms may be suitable.
Unit 1: Algorithmic problem solving 1
,Example:
Example
Write an algorithm to print „Good Morning”
Step 1: Start
Step 2: Print “Good Morning”
Step 3: Stop
2.BUILDING BLOCKS OF ALGORITHMS (statements, state, control flow, functions)
Algorithms can be constructed from basic building blocks namely, sequence,
selection and iteration.
2.1.Statements:
Statement is a single action in a computer.
In a computer statements might include some of the following actions
input data-information given to the program
process data-perform operation on a given input
output data-processed result
2.2.State:
Transition from one process to another process under specified condition with in a
time is called state.
2.3.Control flow:
The process of executing the individual statements in a given order is called control
flow.
The control can be executed in three ways
1. sequence
2. selection
3. iteration
Sequence:
All the instructions are executed one after another is called sequence execution.
Example:
Add two numbers:
Step 1: Start
Step 2: get a,b
Step 3: calculate c=a+b
Step 4: Display c
Step 5: Stop
Selection:
A selection statement causes the program control to be transferred to a specific
part of the program based upon the condition.
If the conditional test is true, one part of the program will be executed, otherwise
it will execute the other part of the program.
Unit 1: Algorithmic problem solving 2
,Example
Write an algorithm to check whether he is eligible to vote?
Step 1: Start
Step 2: Get age
Step 3: if age >= 18 print “Eligible to vote”
Step 4: else print “Not eligible to vote”
Step 6: Stop
Iteration:
In some programs, certain set of statements are executed again and again based
upon conditional test. i.e. executed more than one time. This type of execution is called
looping or iteration.
Example
Write an algorithm to print all natural numbers up to n
Step 1: Start
Step 2: get n value.
Step 3: initialize i=1
Step 4: if (i<=n) go to step 5 else go to step 7
Step 5: Print i value and increment i value by 1
Step 6: go to step 4
Step 7: Stop
2.4.Functions:
Function is a sub program which consists of block of code(set of instructions)
that performs a particular task.
For complex problems, the problem is been divided into smaller and simpler
tasks during algorithm design.
Unit 1: Algorithmic problem solving 3
, Benefits of Using Functions
Reduction in line of code
code reuse
Better readability
Information hiding
Easy to debug and test
Improved maintainability
Example:
Algorithm for addition of two numbers using function
Main function()
Step 1: Start
Step 2: Call the function add()
Step 3: Stop
sub function add()
Step 1: Function start
Step 2: Get a, b Values
Step 3: add c=a+b
Step 4: Print c
Step 5: Return
3.NOTATIONS
3.1.FLOW CHART
Flow chart is defined as graphical representation of the logic for problem solving.
The purpose of flowchart is making the logic of the program clear in a visual
representation.
Unit 1: Algorithmic problem solving 4
ALGORITHMIC PROBLEM SOLVING
Algorithms, building blocks of algorithms (statements, state, control flow, functions),
notation (pseudo code, flow chart, programming language), algorithmic problem
solving, simple strategies for developing algorithms (iteration, recursion). Illustrative
problems: find minimum in a list, insert a card in a list of sorted cards, Guess an
integer number in a range, Towers of Hanoi.
1.PROBLEM SOLVING
Problem solving is the systematic approach to define the problem and creating
number of solutions.
The problem solving process starts with the problem specifications and ends with a
Correct program.
1.1 PROBLEM SOLVING TECHNIQUES
Problem solving technique is a set of techniques that helps in providing logic for solving
a problem.
Problem Solving Techniques:
Problem solving can be expressed in the form of
1. Algorithms.
2. Flowcharts.
3. Pseudo codes.
4. programs
1.2.ALGORITHM
It is defined as a sequence of instructions that describe a method for solving a
problem. In other words it is a step by step procedure for solving a problem.
Properties of Algorithms
Should be written in simple English
Each and every instruction should be precise and unambiguous.
Instructions in an algorithm should not be repeated infinitely.
Algorithm should conclude after a finite number of steps.
Should have an end point
Derived results should be obtained only after the algorithm terminates.
Qualities of a good algorithm
The following are the primary factors that are often used to judge the quality of the
algorithms.
Time – To execute a program, the computer system takes some amount of time. The
lesser is the time required, the better is the algorithm.
Memory – To execute a program, computer system takes some amount of memory
space. The lesser is the memory required, the better is the algorithm.
Accuracy – Multiple algorithms may provide suitable or correct solutions to a given
problem, some of these may provide more accurate results than others, and such
algorithms may be suitable.
Unit 1: Algorithmic problem solving 1
,Example:
Example
Write an algorithm to print „Good Morning”
Step 1: Start
Step 2: Print “Good Morning”
Step 3: Stop
2.BUILDING BLOCKS OF ALGORITHMS (statements, state, control flow, functions)
Algorithms can be constructed from basic building blocks namely, sequence,
selection and iteration.
2.1.Statements:
Statement is a single action in a computer.
In a computer statements might include some of the following actions
input data-information given to the program
process data-perform operation on a given input
output data-processed result
2.2.State:
Transition from one process to another process under specified condition with in a
time is called state.
2.3.Control flow:
The process of executing the individual statements in a given order is called control
flow.
The control can be executed in three ways
1. sequence
2. selection
3. iteration
Sequence:
All the instructions are executed one after another is called sequence execution.
Example:
Add two numbers:
Step 1: Start
Step 2: get a,b
Step 3: calculate c=a+b
Step 4: Display c
Step 5: Stop
Selection:
A selection statement causes the program control to be transferred to a specific
part of the program based upon the condition.
If the conditional test is true, one part of the program will be executed, otherwise
it will execute the other part of the program.
Unit 1: Algorithmic problem solving 2
,Example
Write an algorithm to check whether he is eligible to vote?
Step 1: Start
Step 2: Get age
Step 3: if age >= 18 print “Eligible to vote”
Step 4: else print “Not eligible to vote”
Step 6: Stop
Iteration:
In some programs, certain set of statements are executed again and again based
upon conditional test. i.e. executed more than one time. This type of execution is called
looping or iteration.
Example
Write an algorithm to print all natural numbers up to n
Step 1: Start
Step 2: get n value.
Step 3: initialize i=1
Step 4: if (i<=n) go to step 5 else go to step 7
Step 5: Print i value and increment i value by 1
Step 6: go to step 4
Step 7: Stop
2.4.Functions:
Function is a sub program which consists of block of code(set of instructions)
that performs a particular task.
For complex problems, the problem is been divided into smaller and simpler
tasks during algorithm design.
Unit 1: Algorithmic problem solving 3
, Benefits of Using Functions
Reduction in line of code
code reuse
Better readability
Information hiding
Easy to debug and test
Improved maintainability
Example:
Algorithm for addition of two numbers using function
Main function()
Step 1: Start
Step 2: Call the function add()
Step 3: Stop
sub function add()
Step 1: Function start
Step 2: Get a, b Values
Step 3: add c=a+b
Step 4: Print c
Step 5: Return
3.NOTATIONS
3.1.FLOW CHART
Flow chart is defined as graphical representation of the logic for problem solving.
The purpose of flowchart is making the logic of the program clear in a visual
representation.
Unit 1: Algorithmic problem solving 4
