Algorithms

2. ◦ How to solve a problem.
◦ Algorithm & Pseudo code
◦ Good and Bad Algorithm

3.  At the end of this lecture the student will:
◦ define the term algorithm
◦ state 5 properties of a good algorithm
◦ from a given problem and stated audience, create an
appropriate algorithm using the properties stated above.

4.  Algorithms
 Pseudo code
 Good vs Bad algorithm

5.  An algorithm is a sequence of instructions to be
carried out in order to solve a problem.
or
 It is a step by step procedure to solve a Problem

6.  An algorithm is a part of the plan for the computer
program
 An algorithm is a effective procedure for solving
the problem in a finite number of steps.
 A well designed Algorithm will always provide an
answer.

7.  Example : Write an algorithm to add 2 numbers
 Step 1: Start
 Step 2: Let a=10,b=20
 Step 3: c=a+b;
 Step 4: print c
 Step 5: Stop

8.  First produce a general algorithm (one can use
pseudocode)
 Refine the algorithm successively to get step by
step detailed algorithm that is very close to a
computer language.
 Pseudocode is an artificial and informal
language that helps programmers develop
algorithms. Pseudocode is very similar to
everyday English.

9.  Example 1: Write an algorithm to determine a
student’s final grade and indicate whether it is
passing or failing. The final grade is calculated as
the average of four marks.

10. Pseudocode:
 Input a set of 4 marks
 Calculate their average by summing and
dividing by 4
 if average is below 50
Print “FAIL”
else
Print “PASS”

11.  Detailed Algorithm
 Step 1: Input M1,M2,M3,M4
Step 2: GRADE ← (M1+M2+M3+M4)/4
Step 3: if (GRADE < 50) then
Print “FAIL”
else
Print “PASS”
endif

12.  All algorithms will have input, perform a process,
and produce output.
 A good algorithm should be:
◦ Simple - relative
◦ Complete – account for all inputs & cases
◦ Correct (Right)
◦ should have appropriate levels of Abstraction. –
grouping steps into a single module
◦ Precise

13.  Sequence
 Decision
 Repetition

14.  It means that each step or process in the algo is
executed in the specified order.

15.  In algorithm the result of the decision is either true
or false not state in between.
 Example
 If today is Sunday then it is a holiday

16.  This can be implemented using loops.

17. Drivethecarto
school
Get directions
Start the car
Follow the directions
Get parking pass
Drive to the
destination
Turn left out of your
driveway
At the next light, turn right.
At the intersection with I-
66, take the on-ramp for
I-66 West
…
Level 1
Level 2
Level 3Find a place to park
Stop the car

18. 1. Start
2. Input A and B
3. If A>B then
 Print “A is Greater than B”
4. If B> A then
 Print “B is Greater than A”
5. If A==B then
 Print “Both are Equal”
6. Stop

19. 1. Start
2. Print Enter any 2 values
3. Input A and B
4. C=A
5. A=B
6. B=C
7. Print A,B
8. Stop

20.  Analyze the problem and develop the
specification.
 Design the solution
◦ Test the solution as part of the design steps.
 Implement the program (code the program)
 Test the program
 Validate the program (further extensive testing)
to insure it works under all circumstances.

21.  Now you can easily make an algorithm and that
algorithm must be good one as discussed by
Shaum’s

22. Q1)_______ is a procedure or step by step process
for solving a problem.
A. Algorithm
B. Flowchart
C. Pseudocode
D. All of these
Q2) According to shaum which is the first step?
A. Designing
B. Testing
C. Validating
D. Analyzing the problem

23. Q3) The list of coded instructions is called?
A. Algorithm
B. Computer Program
C. Pseudocode
D. All of these
Q4) Algorithms are used for ?
A. Better Programming
B. Efficient Coding
C. Easy testing
D. All of these

24. Q5 Which of the following is not a characteristic of
good algorithm?
(a) Precise
(c) Ambiguous
(b) Finite number of steps
(d) Logical flow of control

25.  Programming in C ‘ ABS PUBLICATIONS’