1. Computer Science Department
Algorithm
Knowledge:
Understand algorithm representation using flowchart and pseudocode
Skill:
Map problem to solution in flowchart and pseudocode forms
FTSM
Computer Science Department

2. Algorithm in Real Life Consider the following ….
Problem: Baking a Cake
How to solve:
Start
Preheat the oven at 180oC
Prepare a baking pan
Beat butter with sugar
Mix them with flour, eggs and essence vanilla
Pour the dough into the baking pan
Put the pan into the oven
End
TK1913-C Programming

3. ‘Divide and Conquer’ Strategy in Algorithm
Problem: Prepare a Breakfast
1. Start
2. Prepare a Breakfast
3. End
TK1913-C Programming

4. ‘Divide and Conquer’ Strategy in Algorithm
1. Start
2. Prepare a Breakfast
2.1 Prepare a tuna sandwich
2.2 Prepare some chips
2.3 Make a cup of coffee
3. End
TK1913-C Programming

5. ‘Divide and Conquer’ Strategy in Algorithm
1. Start
2. Prepare a Breakfast
2.1 Prepare a tuna sandwich
2.1.1 Take 2 slices of bread
2.1.2 Prepare tuna paste
2.2 Prepare some chips
2.3 Make a cup of coffee
3. End
TK1913-C Programming

6. ‘Divide and Conquer’ Strategy in Algorithm
1. Start
2. Prepare a Breakfast
2.1 Prepare a tuna sandwich
2.1.1 Take 2 slices of bread
2.1.2 Prepare tuna paste
2.2 Prepare some chips
2.2.1 Cut potatoes into slices
2.2.2 Fry the potatoes
2.3 Make a cup of coffee
3. End
TK1913-C Programming

7. ‘Divide and Conquer’ Strategy in Algorithm
1. Start
2. Prepare a Breakfast
2.1. Prepare a tuna sandwich
2.1.1 Take 2 slices of bread
2.1.2 Prepare tuna paste
2.2. Prepare some chips
2.2.1 Cut potatoes into slices
2.2.2 Fry the potatoes
2.3. Make a cup of coffee
2.3.1 Boil water
2.3.2 Add water with sugar and coffee
3. End
TK1913-C Programming

8. Something to ponder …
What is the connection between these real life processes and algorithm?
TK1913-C Programming

9. Algorithm
A specific and step-by-step set of instructions for carrying out a procedure or solving a problem, usually with the requirement that the procedure terminate at some point
2 types of algorithm representation will be explained:
Flowchart
Pseudocode
Structured Method (will be explained later)
A method of designing problem solution
TK1913-C Programming

10. Flowchart
Flowchart represents algorithm graphically. It is intended for communication and documentation
TK1913-C Programming

11. Flowchart – Basic Syntax
Start/End
Symbol
Semantic
Process
Input/Output
Test
Connector
Flow of activities
TK1913-C Programming

12. Flowchart – Other Syntax
Function call
Symbol
Semantic
Magnetic Disc
Stored Data
Document/File
Multiple Document/File
TK1913-C Programming

13. Something to ponder …
Are the steps in the algorithm discussed earlier specific enough to be executed by computer?
TK1913-C Programming

14. Problem Solving Process
Input
Process
Output
TK1913-C Programming

15. Example 1
Calculate and display the price of a number of apples if the quantity in kg and price per kg are given.
Input
Process
Output
Quantity
Price_per_kg
Price = Quantity * Price_per_kg
Price
TK1913-C Programming

16. Flowchart: Calculate Price of Apples
Start
Input
Quantity
Input
Price_per_kg
Price  Quantity * Price_per_kg
Output
Price
End
TK1913-C Programming

17. C Program: Calculate Price of Apples
Input
Quantity
Start
Price  Quantity * Price_per_kg
Price_per_kg
Output
Price
End
void main() {
scanf(“%d”,&quantity);
scanf(“%d”,&price_per_kg);
price = quantity*price_per_kg;
printf(“%d”, price); }
TK1913-C Programming

18. C Program: Calculate Price of Apples
void main() {
scanf(“%d”,&quantity);
scanf(“%d”,&price_per_kg);
price = quantity*price_per_kg;
printf(“%d”, price); }
It’s not complete! Declare the variables…
TK1913-C Programming

19. C Program: Calculate Price of Apples
void main() {
int quantity, price_per_kg, price;
scanf(“%d”,&quantity);
scanf(“%d”,&price_per_kg);
price = quantity*price_per_kg;
printf(“%d”, price); }
Well done ! But…what are they?
TK1913-C Programming

20. C Program: Calculate Price of Apples
void main() {
int quantity, price_per_kg, price;
scanf(“%d”,&quantity);
scanf(“%d”,&price_per_kg);
price = quantity*price_per_kg;
printf(“%d”, price); }
Start
Declaration }
Input
Process
Output
End
TK1913-C Programming

21. C Program: Calculate Price of Apples
void main() {
int quantity, price_per_kg, price;
scanf(“%d”,&quantity);
scanf(“%d”,&price_per_kg);
price = quantity*price_per_kg;
printf(“%d”, price); }
Chapter 4 }
Chapter 5
Chapter 6
Chapter 5
TK1913-C Programming

22. Example 2 ???? Process A car park has the following charges:
The 1st hour costs RM2.00. The subsequent hours cost RM1.00 per hour. Write an algorithm based on a vehicle’s entry and exit time.
Input
Process
Output
Entry_time
Exit_time
????
Charge
TK1913-C Programming

23. Flowchart: Calculate Car Park Charge
Start
Input Entry_time
Input Exit_time
Period  Exit_time – Entry_time
Period > 1? No
Yes
Charge 2
Charge  2 + (Period * 1)
Output
Charge
End
TK1913-C Programming

24. Flowchart: Calculate Car Park Charge
Input Entry_time
Input Exit_time
Start
Output
Charge
End
Period  Exit_time – Entry_time
Period > 1?
Yes
Charge  2 + (Period * 1)
Charge 2 No
scanf(“%d%d”,&entry_time,&exit_time);
period = exit_time – entry_time;
if (period > 1)
charge = 2 + ( period *1);
else
charge = 2;
printf(“%d”,charge);
TK1913-C Programming

25. C Program: Calculate Car Park Charge
void main() {
int entry_time, exit_time, period, charge;
scanf(“%d%d”,&entry_time,&exit_time);
period = exit_time – entry_time;
if (period > 1)
charge = 2 + (period * 1);
else
charge = 2;
printf(“%d”,charge); } }
Chapter 7
TK1913-C Programming

26. Example 3
Write a program to calculate the average mark of three TK1913’s students.
Input
Process
Output
Mark A
Mark B
Mark C
????
Average_mark
THINK!!
TK1913-C Programming

27. Algorithm Development Guidelines
Identify the input and output of the problem.
If necessary, use ‘Divide & Conquer’ strategy to decompose the problem into smaller and manageable sub problems. Decompose the problem until all the sub problems can be solved to get the required results
For each sub problem, identify and list out the steps involved in solving it
TK1913-C Programming

28. Something to ponder … What might be the disadvantage of flowchart?
TK1913-C Programming

29. Pseudocode
An outline of a program, written in a form that can easily be converted into real programming statements. It resembles the actual program that will be implemented later. However, it cannot be compiled nor executed.
Pseudocode normally codes the following actions:
Initialisation of variables
Assignment of values to the variables
Arithmetic operations
Relational operations
TK1913-C Programming

30. Example of Pseudocode 1. Start 2. Read quantity 3. Read price_per_kg
4. price  quantity * price_per_kg
5. Print price
6. End
TK1913-C Programming

31. Guidelines on Writing Pseudocode
Refer to the handouts in your manual …. OK??
TK1913-C Programming

32. CFlow Demonstration
TK1913-C Programming

33. End of Lecture 2 Yes !! That’s all? What’s next???
INTRODUCTION TO C on the way …
TK1913-C Programming