Lecture 12 - Control Structures Rep Pt 1.pdf

8/14/2019 Lecture 12 - Control Structures Rep Pt 1.pdf

1/20

2/13/201

1992-2012 by Pearson Education, Inc. & John Wiley & SonsSome portions are adopted from C++ f or Everyone by Horstmann

ENGR 1200U Introduction to Programming

Lecture 12

Control Structures: Repetition (Chapter 4)

Dr. Eyhab Al-Masri

ENGR 1200UWinter 2013 - UOIT

In Chapter 3, we developed algorithms that usedselection control structures Provide alternative paths during program execution

In this chapter, we develop algorithms and writeC++ programs that use repetition structures

Whatisarepetitionstructure?Repetition structure allows us to repeat (or loop

through) a set of steps as long as the condition is true


2/20

2/13/201


Example We might want to compute the average of midterm

exam grades.

Howtoentermidtermgrades?Use a repetition control structure to request the user

to enter the midterm grades until a condition becomesfalse (i.e. no more students). Through every loop (i.e.

every new grade entered), calculate the sum anddivide by number of students (i.e. iterations)


Algorithms usingrepetition structurescan be describedwith pseudocode orflowcharts

is count


3/20

2/13/201


Loops are used to implement repetitionstructures

C++ contains three different loop structures

C++ also supports t two additional statementswith loops to modify their performance:

while for do/while

break continue


Syntax:while (boolean_expression)statement; while (boolean_expression) {statement1;statement_n;}Exampleswhile (!isspace(ch))

cin.get(ch); // statement repeated until a// space character is read

while (x>y) { //statement block executed//while x>0

++count;--x;

}


4/20

2/13/201


An investment Problem: Savings account start balance: $10,000 Task: How many years until we have at least $20,000?1. Set a year value to 0, set a balance value to $10,000

2. Repeat the following steps while balance is less than$20,000

Increment the year value by 1

Compute the interest by multiplying balance value by 0.05(5% interest)

Add interest to balance

3. Report final year value as the answer

Yes!

Algorithm:

C++ for Everyone by Cay Horstman


The statements to be controlled are:

Incrementing the year variable

Computing the interest variable using interest 5%

Updating the balance variable by adding the interest

year++;

double interest = balance * (5/100);balance = balance + interest;

Yes!

code snippet:



5/20

2/13/201


The condition which indicates whento stop executing the statements isthis test

(balance < TARGET)

while (balance < TARGET)

{

year++;

double interest = balance * RATE / 100;

balance = balance + interest;}

Yes!

complete while statement



Notice that interest is defined insidethe loop and that year and balanceare defined outside the loop

while (balance < TARGET)

{

year++;

double interest = balance * RATE / 100;

balance = balance + interest;

}

Yes!

complete while statement

A new interest variable to be created in each iteration.year and balance are used for all iterations.



6/20

2/13/201

ENGR 1200UWinter 2013 - UOIT C++ for Everyone by Cay Horstman


int main(){

const double RATE=5;

const double INITIAL_BALANCE=10000;

const double TARGET=2*INITIAL_BALANCE;

double balance=INITIAL_BALANCE;

int year=0;

while (balance


7/20

2/13/201


10000

0


10000

0

10000

0

?


8/20

2/13/201


10000

1

10000

1

?


10000

1

10000

1

500


9/20

2/13/201


10500

1

10500

1

500


10500

1

10500

1

500


10/20

2/13/201

1


10500

1


10500

1

10500

1

?


11/20

2/13/201

1


10500

2

10500

2

?


10500

2

10500

2

525


12/20

2/13/201

1


11025

1

11025

525

2


10500

1

11025

525

2


13/20

2/13/201

1


11025

2


this process goes onfor 15 iterations

before entering while's

b od y at t he en d o f w hi le' s bo dy

balance year interest balance year

10000.00 0 500.00 10500.00 1

10500.00 1 525.00 11025.00 2

11025.00 2 551.25 11576.25 3

11576.25 3 578.81 12155.06 4

12155.06 4 607.75 12762.82 5

12762.82 5 638.14 13400.96 6

13400.96 6 670.05 14071.00 7

14071.00 7 703.55 14774.55 8

14774.55 8 738.73 15513.28 9

15513.28 9 775.66 16288.95 10

16288.95 10 814.45 17103.39 1 1

17103.39 11 855.17 17958.56 1 2

17958.56 12 897.93 18856.49 1 3

18856.49 13 942.82 19799.32 1 4

19799.32 14 989.97 20789.28 1 5

20789.28 15 w hi le s tat em en t i s o ver


14/20

2/13/201

1






10000.00 0 500.00 10500.00 1

10500.00 1 525.00 11025.00 2

11025.00 2 551.25 11576.25 3

11576.25 3 578.81 12155.06 4

12155.06 4 607.75 12762.82 5

12762.82 5 638.14 13400.96 6

13400.96 6 670.05 14071.00 7

14071.00 7 703.55 14774.55 8

14774.55 8 738.73 15513.28 9

15513.28 9 775.66 16288.95 10

16288.95 10 814.45 17103.39 1 1

17103.39 11 855.17 17958.56 1 2

17958.56 12 897.93 18856.49 1 3

18856.49 13 942.82 19799.32 1 4

19799.32 14 989.97 20789.28 1 5







10000.00 0 500.00 10500.00 1

10500.00 1 525.00 11025.00 2

11025.00 2 551.25 11576.25 3

11576.25 3 578.81 12155.06 4

12155.06 4 607.75 12762.82 5

12762.82 5 638.14 13400.96 6

13400.96 6 670.05 14071.00 7

14071.00 7 703.55 14774.55 8

14774.55 8 738.73 15513.28 9

15513.28 9 775.66 16288.95 10

16288.95 10 814.45 17103.39 1 1

17103.39 11 855.17 17958.56 1 2

17958.56 12 897.93 18856.49 1 3

18856.49 13 942.82 19799.32 1 4

19799.32 14 989.97 20789.28 1 5



15/20

2/13/201

1






10000.00 0 500.00 10500.00 1

10500.00 1 525.00 11025.00 2

11025.00 2 551.25 11576.25 3

11576.25 3 578.81 12155.06 4

12155.06 4 607.75 12762.82 5

12762.82 5 638.14 13400.96 6

13400.96 6 670.05 14071.00 7

14071.00 7 703.55 14774.55 8

14774.55 8 738.73 15513.28 9

15513.28 9 775.66 16288.95 10

16288.95 10 814.45 17103.39 1 1

17103.39 11 855.17 17958.56 1 2

17958.56 12 897.93 18856.49 1 3

18856.49 13 942.82 19799.32 1 4

19799.32 14 989.97 20789.28 1 5







10000.00 0 500.00 10500.00 1

10500.00 1 525.00 11025.00 2

11025.00 2 551.25 11576.25 3

11576.25 3 578.81 12155.06 4

12155.06 4 607.75 12762.82 5

12762.82 5 638.14 13400.96 6

13400.96 6 670.05 14071.00 7

14071.00 7 703.55 14774.55 8

14774.55 8 738.73 15513.28 9

15513.28 9 775.66 16288.95 10

16288.95 10 814.45 17103.39 1 1

17103.39 11 855.17 17958.56 1 2

17958.56 12 897.93 18856.49 1 3

18856.49 13 942.82 19799.32 1 4

19799.32 14 989.97 20789.28 1 5



16/20

2/13/201

1



until thebalance is

finally(!) over $20,000 andthe test becomes false.




10000.00 0 500.00 10500.00 1

10500.00 1 525.00 11025.00 2

11025.00 2 551.25 11576.25 3

11576.25 3 578.81 12155.06 4

12155.06 4 607.75 12762.82 5

12762.82 5 638.14 13400.96 6

13400.96 6 670.05 14071.00 7

14071.00 7 703.55 14774.55 8

14774.55 8 738.73 15513.28 9

15513.28 9 775.66 16288.95 10

16288.95 10 814.45 17103.39 1 1

17103.39 11 855.17 17958.56 1 2

17958.56 12 897.93 18856.49 1 3

18856.49 13 942.82 19799.32 1 4

19799.32 14 989.97 20789.28 1 5



15


17/20

2/13/201

1




18/20

2/13/201

1



What is the output of thefollowing while loop?

i =5;

while (i >0)

{

cout


19/20

2/13/201

1



i =5;

while (i >0)

{

cout


20/20

2/13/201



i =5;

while (i

Lecture 12 - Control Structures Rep Pt 1.pdf

Documents