Problem solving and programming control structures.pptx

Problem Solving, pseudocode and flowchart

1. Programming Approach in Problem Solving

2. 1. 1 Approach in Problem Solving 1.1.1 Input Process Output (IPO) Analysis

3. Learning Outcome Identify input, process and output from a given problem

4. Input Process Output (IPO) Analysis The IPO is used to analyze problems and develop algorithms Used to organize and summarize the results of a problem analysis It shows where in the solution the processing takes place

5. Input Process Output (IPO) Analysis Input Processing Output Processing items: Algorithm It can also be represent using IPO chart

6. Input Process Output (IPO) Analysis Identify Input : Process : Output : To do the IPO Analysis , start with: Output (Display the results) Input (Read the data) Process (Perform the computation)

7. Input Process Output (IPO) Analysis Output should answer the following question: What does the user want to see printed on the printer, displayed on the screen, or stored in a file?

8. Input Process Output (IPO) Analysis Input should answer the following question: What information will the computer need to know to print, display, or store the output items?

9. Input Process Output (IPO) Analysis Processing item: An intermediate value that the algorithm uses when processing the input into the output

10. Analyze the Problem What is it you are trying to accomplish? What outcome are you trying to arrive at? List the Inputs and Outputs Often you work backwards from the Output List the Outputs, and then figure out what Inputs you need in order to arrive at the Outputs

11. follows Example 1 Problem statement: Calculate the area of a rectangle We can summarize the information contained in the problem statement as Analyze the Problem height width

12. Problem Analysis: Identify : INPUT : PROCESS : OUTPUT : To do the IPO Analysis, start with: – Output – Input – Process Analyze the Problem

13. Analyze the Problem Problem Analysis: Input: width, height Process: area = width x height Output: area of rectangle

14. Input width height Analyze the Problem Processing Processing items: area = width x height Algorithm : Output area of rectangle The Problem Analysis , can also be represent using IPO (Input, Processing, Output) Chart

15. Analyze the Problem Example 2 Problem statement: Find the average of three numbers input by user We can summarize the information contained in the problem statement as follows

16. Problem Analysis: Identify : INPUT : PROCESS : OUTPUT : To do the IPO Analysis, start with: – Output – Input – Process Analyze the Problem

17. Analyze the Problem Problem Analysis: Input: number1, number2, number3 Process: average = (number1 + number2 + number3) / 3 Output: average

18. Input number1 number2 number3 Analyze the Problem Processing Processing items: average = (number1 + number2 + number3) / 3 Algorithm : Output average The Problem Analysis , can also be represent using IPO (Input, Processing, Output) Chart

19. Analyze the Problem Example 3 Problem statement: Determine the total cost of apples, given the number of kilos of apples purchased and the cost of apples per kilo We can summarize the information contained in the problem statement as follows

20. Problem Analysis: Identify : INPUT : PROCESS : OUTPUT : To do the IPO Analysis, start with: – Output – Input – Process Analyze the Problem

21. Analyze the Problem Problem Analysis: Input: Number of kilos of apples Cost of apples per kilo Process: Total cost = Number of kilos of apples × Cost of apples per kilo Output: Total cost of apples

22. Analyze the Problem The Problem Analysis , can also be represent using IPO (Input, Processing, Output) Chart Input Number of kilos of apples Cost of apples per kilo Processing Processing items: Total cost = Number of kilos of apples × Cost of apples per kilo Algorithm : Output Total cost of apples

23. Summary What have you learned ? Approaches in problem solving Identify Input Process Output (IPO) from a problem statement

24. Approach in Problem Solving 1.1.2 Algorithm 1. 1.3 Pseudocode

25. Learning Outcome Define algorithm Solve problem using pseudocode

26. ALGORITHM The algorithm is the abstract idea of solving a problem. An algorithm is a step- by-step instructions that will transform the input into the output It can be represent using pseudocode or flow chart

27. From Algorithms to Programs Problem C++ Program Problem Analysis Algorithm

28. Algorithm in everyday’s life How to make a mug of hot coffee: Start Boil water Prepare a mug Put a tea spoon of coffee & sugar Pour hot water Stir End

29. can be described using three control structures (Bohm and Jacopini- 1966); A Sequence o is a series of statements that execute one after another A Selection – (branch) o statement is used to determine which of two different statements to execute depending on certain conditions A Looping – (repetition) stateme n t is used to repeat statements while certain conditions are met ALGORITHM

30. PLANNING THE ALGORITHM Transfer to pseudo code or flow chart a. Must start with a start b. Must close with an end 1. Do Problem Analysis Identify: INPUT : PROCESS : OUTPUT :

31. TECHNIQUES TO REPRESENT THE ALGORITHM Similar to everyday English Flow chart Graphical representation of an algorithm Special- purpose symbols connected by arrows (flow lines) 1.Pseudocod e 2. Flow chart Artificial , informal language used to develop algorithms Pseudocode

32. TECHNIQUES TO REPRESENT THE ALGORITHM Pseudocode Start: Input radius Calculate circle area circle area = 3.142 * radius * radius Print the circle area End: 1. Example of Pseudocode & Flow chart Calculate the area of a circle radius circle area = 3.142 * radius * radius circle area Flow chart start end

33. 1. Pseudocode - Pseudocode Format start statement 1 statement 2 end TECHNIQUES TO REPRESENT THE ALGORITHM 1 3 2

34. Algorithm Design : Pseudocode Example 1 Problem statement: Calculate the area of a rectangle Remember! Do Problem Analysis Transfer to pseudo code or flow chart

35. Algorithm Design : Pseudocode 1. Problem Analysis: Input: width, height Process: area = width x height Output: area of rectangle

36. Algorithm Design : Pseudocode 2. Pseudocode start read width and height calculate area area of rectangle = width * height print area of rectangle end

37. IPO Chart with Pseudocode Input width height Processing Processing items: area = width x height Algorithm - Pseudocode: Start Read width and height Calculate area area of rectangle = width * height Print area End Output area of rectangle

38. Algorithm Design : Pseudocode Example 2 Problem statement: Find the average of three numbers input by user Remember! Do Problem Analysis Transfer to pseudo code or flow chart

39. Algorithm Design : Pseudocode 1. Problem Analysis: Input: number1, number2, number3 Process: average = (number1 + number2 + number3) / 3 Output: average

40. Algorithm Design : Pseudocode start input number1, number2, number3 calculate average average = (number1 + number2 + number3) / 3 print average end 2. Pseudocode

41. 2/10/12 IPO Chart with Pseudocode Input number1 number2 number3 Processing Processing items: average = (number1 + number2 + number3) / 3 Algorithm - Pseudocode: Start Input number1, number2, number3 Calculate average average = (number1 + number2 + number3) / 3 Print average End Output average

42. Algorithm Design : Pseudocode Example 3 Problem statement: Determine the total cost of apples, given the number of kilos of apples purchased and the cost of apples per kilo Remember! Do Problem Analysis Transfer to pseudo code or flow chart

43. Algorithm Design : Pseudocode 1. Problem Analysis: Input: Number of kilos of apples Cost of apples per kilo Process: Total cost = Number of kilos of apples × Cost of apples per kilo Output: Total cost of apples

44. 02/10/12 Algorithm Design : Pseudocode 2. Pseudocode start Read Number of kilos of apples and Cost of apples per kilo Calculate Total cost Total cost = Number of kilos of apples x Cost of apples per kilo Print Total cost of apples end

45. 2/10/12 Input Number of kilos of apples Cost of apples per kilo Processing Total cost = Number of kilos of apples × Cost of apples per kilo Algorithm - Pseudocode: Start Read Number of kilos of apples and Cost of apples per kilo Calculate Total Cost Total cost = Number of kilos of apples × Cost of apples per kilo Print Total cost of apples End Output Total cost of apples IPO Chart with Pseudocode

46. Summary What have you learned ? Approaches in problem solving Planning the algorithm Steps in building pseudocode Problem solving using pseudocode

47. Approach in Problem Solving Flow Chart

48. Learning Outcome Solve problem using flow chart

49. TECHNIQUES TO REPRESENT THE ALGORITHM Statement 1 Statement 2 2. Flow Chart - Flow Chart Format start The statement refers to any input, output & process involved end

50. 02/10/12 FLOW CHART - SYMBOLS Graphic Symbol Name Meaning Terminal indicates the beginning and end Symbol (oval) points of an algorithm Process Symbol (rectangle) shows an instruction other than input, output or selection Input-Output Symbol (parallelogram) shows an input or output operation

51. 02/10/12 FLOW CHART - SYMBOLS Graphic Symbol Name Meaning Disk Storage Input- Output Symbol (cylinder) indicates input from or output to disk storage Printer Output Symbol shows hardcopy printer output (diamond) Selection Symbol shows a selection process for two- way selection

52. FLOW CHART - SYMBOLS Graphic Symbol Name Meaning Flow Lines (arrow) indicates the logical sequence of execution steps in the algorithm Off- Page Connector provides continuation of a logical path on another page On- Page Connector (circle) provides continuation of a logical path at another point in the same page

53. Algorithm Design : Flow Chart Example 1 Problem statement: Calculate the area of a rectangle Remember! Do Problem Analysis Transfer to pseudo code or flow chart

54. Algorithm Design : Flow Chart 1. Problem Analysis: Input: width, height Process: area = width x height Output: area of rectangle

55. Algorithm Design : Flow Chart 2. Flow Chart start width, height area = width * height area end

56. 2/10/12 IPO Chart with Flow Chart Input width height Processing Processing items: area = width x height Output area of rectangle Algorithm – Flow Chart: start width, height area = width * height area end

57. Algorithm Design : Flow Chart Example 2 Problem statement: Find the average of three numbers input by user Remember! Do Problem Analysis Transfer to pseudo code or flow chart

58. Algorithm Design : Flow Chart 1. Problem Analysis: Input: number1, number2, number3 Process: average = (number1 + number2 + number3) / 3 Output: average

59. Algorithm Design : Flow Chart 2. Flow Chart start number1, number2, number3 average = (number1 + number2 + number3) / 3 average end

60. 02/10/12 IPO Chart with Flow Chart Input number1 number2 number3 Processing Processing items: average = (num1 + num2 + num3) / 3 Output average Algorithm – Flow Chart: start number1, number2, number3 average = (number1 + number2 + number3) / 3 average end

61. Algorithm Design : Flow Chart Example 3 Problem statement: Determine the total cost of apples, given the number of kilos of apples purchased and the cost of apples per kilo Remember! Do Problem Analysis Transfer to pseudo code or flow chart

62. Algorithm Design : Flow Chart 1. Problem Analysis: Input: Number of kilos of apples Cost of apples per kilo Process: Total cost = Number of kilos of apples × Cost of apples per kilo Output: Total cost of apples

63. Algorithm Design : Flow Chart Number of kilos of apples, Cost of apples per kilo Total cost = Number of kilos of apples x Cost of apples per kilo Total cost of apples 2. Flow Chart start end

64. 2/10/12 IPO Chart with Flow Chart Input Number of kilos of apples Cost of apples per kilo Processing Total cost = Number of kilos of apples × Cost of apples per kilo Algorithm – Flow Chart: Output Total cost of apples end start Number of kilos of apples, Cost of apples per kilo Total cost = Number of kilos of apples x Cost of apples per kilo Total cost of apples

65. Summary What have you learned ? Approaches in problem solving Steps in building flow chart Problem solving using flow chart

66. Revision What have you learned ? What is IPO analysis? What is algorithm? What are the steps in planning your algorithm? Differentiate between pseudocode and flowchart.

67. Approach in Problem Solving 1.2 Control Structure 1.2.1 Sequence

68. SEQUENCE Control Structures SELECTION LOOPING

69. Sequence Learning Outcome At the end of the lesson, students should be able to : Understand basic problem solving techniques. Use the sequence structured in problem solving. Develop flowchart through the process of top-down.

70. Sequence The simplest programs consist just sequence of statements : no loops, no selections amongst alternative actions, no use of subroutines.

71. Sequence Instruction in sequence programming are executed sequentially one by one The sequence structure directs the computer to process the instructions, one after another, in the order listed in the program. first instruction last instruction.

72. Sequence

73. Sequence Planning the Algorithm Record the algorithm using IPO analysis / IPO chart. Problem Analysis: Input: sales Process: bonus = sales * (0.05) Output: bonus

74. Algorithm Design : Pseudocode Pseudocode - tool programmers use to help them plan an algorithm - consist of short, English- like statements start input sales bonus = sales * (0.05) print bonus end

75. Algorithm Design : Flow Chart Flow Chart - Use standardized symbols to show the steps the computer need to take to accomplish the program’s goal start end sales bonus = sales * (0.05 ) bonus

76. Sequence

77. 8.2.5.1 Sequence Planning the Algorithm Record the algorithm using IPO analysis / IPO chart. Problem Analysis: Input: width, length, price of tile Process: area = width * length total of price = area * price of tile Output: total of price

78. Algorithm Design : Pseudocode Pseudocode - tool programmers use to help them plan an algorithm - consist of short, English- like statements start input width, length, price of tile area = width * length total price of tile = area * price of tile print total price of tile end

79. Algorithm Design : Flow Chart start end width length price of tile area = width * length total price of tile = area * price of tile Total price of tile Flow Chart - Use standardized symbols to show the steps the computer need to take to accomplish the program’s goal

80. Sequence

81. 8.2.5.1 Sequence Planning the Algorithm Record the algorithm using IPO analysis / IPO chart. Problem Analysis: Input: hour Process: Total overtime payment = hour * 5.00 Output: total overtime payment

82. Algorithm Design : Pseudocode Pseudocode - tool programmers use to help them plan an algorithm - consist of short, English- like statements start input hour total overtime payment = hour * 5.00 print total overtime payment end

83. Algorithm Design : Flow Chart start hour Total overtime payment = hour * 5.00 Total overtime payment end Flow Chart - Use standardized symbols to show the steps the computer need to take to accomplish the program’s goal

84. Summary Instruction in sequence programming are executed sequentially one by one First step in the problem- solving process it to analyze the problem Planning the algorithm is using IPO analysis / IPO chart Programmer uses the pseudocode as a guide when coding the algorithm Flow chart uses standardized symbols to show the steps the computer needs to take to accomplish the program’s goal

85. Approach in Problem Solving 1.2 Control Structure 1.2.2 Selection

86. Learning Outcome At the end of this topic, students should be able to: explain the purpose of selection control structure. apply selection control structure in problem solving.

87. Control Structure : Selection SELECTION Analogy You need to choose to make “Coffee O” or “Milk Coffee”

88. Control Structure : Selection SEQUENC E Control Structures SELECTION LOOPING

89. Control Structure : Selection What is Selection Structure? The selection structure allows instructions to be executed non-sequentially. It allows the comparison of two expressions, and based on the comparison, to select certain course of action.

90. Control Structure : Selection if- else Types of selection structure nested if- else switch if-else-if

91. Selection  (1) if-else If- else structure’s form if (expression) statement_1 else statement_2

92. Selection  (1) if-else In this form, the expression is first evaluated. If it evaluates to non- zero (TRUE), statement_1 is executed. Otherwise, statement_2 is executed. Either statement_1 or statement_2 is executed but not BOTH.

93. Selection  (1) if-else Pseudocode format: start if (expression) statement_1 else statement_2 end

94. Flow chart format: Selection  (1) if-else

95. Selection  (1) if-else Example 1: Print “Excellent!” when user enter marks greater than and equal to 80, else print “Sorry, try again”. Remember to plan your algorithm! 1.Do IPO Analysis Transfer to Pseudocode or Flow Chart

96. Selection  (1) if-else Example 1: Print “Excellent!” when user enter marks greater than and equal to 80 , else print “Sorry, try again”.

97. Selection  (1) if-else IPO Analysis : Input: marks Process: if (marks >= 80) print “Excellent” else print “Sorry, try again” Output: “Excellent!” or “Sorry, try again”

98. Selection  (1) if-else Pseudocode start read marks if (marks >= 80) print “Excellent!” else print “Sorry, try again” end

99. end Selection  (1) if-else Flow chart start marks marks >= 80 true “Excellent!” “Sorry, try again” false

100. Selection  (1) if-else Example 2: A high school poetry competition is open only for students above 15 years old. Display “Eligible” if the students meet the requirement, else display “Not eligible” if otherwise.

101. Selection  (1) if-else Example 2: A high school poetry competition is open only for students above 15 years old . Display “Eligible” if the students meet the requirement, else display “Not eligible” if otherwise.

102. Selection  (1) if-else IPO Analysis : Input: age Process: if (age > 15) print “Eligible” else print “Not eligible” Output: “Eligible” or “Not eligible”

103. Selection  (1) if-else Pseudocode start read age if (age > 15) print “ Eligible” else print “ Not eligible ” end

104. end Selection  (1) if-else Flow chart start age age > 15 true “Eligible” “Not eligible” false

105. Selection  (1) if-else Example 3: If x is greater than y, display “x is bigger than y” else display “x is smaller than y”.

106. Selection  (1) if-else Example 3: If x is greater than y , display “x is bigger than y” else display “x is smaller than y”.

107. Selection  (1) if-else IPO Analysis : Input: x,y Process: if (x > y) print “x is bigger than y” else print “x is smaller than y” Output: “x is bigger than y” OR “x is smaller than y”

108. Selection  (1) if-else Pseudocode start read x,y if (x > y) print “ x is bigger than y” else print “ x is smaller than y ” end

109. end Selection  (1) if-else Flow chart start x,y x > y true “x is bigger than y” “x is smaller than y” false

110. Selection  (2) nested if- else if- else Types of selection structure nested if- else switch if-else-if

111. Selection  (2) if- else …IF The if- else structure can also be nested to any depth.

112. Selection  (2) if- else …If The nested if- else if structured takes the general form: if (expression_1) statement_1; else if (expression_2) statement_2; else if (expression_3) statement_3; else statement_4;

113. In this nested form, expression_1 is evaluated. If it evaluates to non- zero (TRUE), statement_1 is executed. If not, control goes to the second if, where expression_2 is evaluated. If it evaluates to non- zero (TRUE), statement_2 is executed. If not, control goes to the third if, where expression_3 is evaluated. If it evaluates to non- zero (TRUE), statement_3 is 02 / 1 e / 1 x 2 e cu t e d. Selection  (2) if- else…If

114. Selection  (2) if- else…If If not, statement_4 is executed. Rules  Only ONE of the statements is executed.

115. Selection  (2) if- else…If Example 1: if student’s grade is greater than or equal to 80 Print “A” else if student’s grade is greater than or equal to 60 Print “B” else if student’s grade is greater than or equal to 50 Print “C” else Print “Failed”

116. Selection  (2) if- else…If IPO Analysis : Input: grade Process: if (grade >= 80) print “A” else if (grade >= 60) print “B” else if (grade >= 50) print “C” else print “Failed” Output: “A” or “B” or “C” or “Failed”

117. Selection  (2) if- else…If Pseudocode start read grade if (grade >= 80) print “A” else if (grade >= 60) print “B” else if (grade >= 50) print “C” else print “Failed” end

118. Selection  (2) if- else…If end Flow chart start grade true “A” “B” “C” grade >= 80 false grade >= 60 false grade >= 50 false “Failed” true true

119. Selection  (2) if- else…If Example 2: if (x > 0) display "x is positive" else if (x < 0) display "x is negative" else display "x is 0"

120. Selection  (2) if- else…If IPO Analysis : Input: x Process: if (x > 0) display "x is positive" else if (x < 0) display "x is negative" else display "x is 0“ Output: “ x is positive“ or "x is negative“ or “ x is 0”

121. Selection  (2) if- else…If Pseudo code start read x if (x > 0) display "x is positive" else if (x < 0) display "x is negative" else display "x is 0" end

122. Selection  (2) if- else…If Flow chart start x true "x is positive” “x is negative” (x > 0) false (x < 0) false “ x is ” end true

123. Selection  (3) Nested If else if- else Types of selection structure nested if- else switch if-else-i f

124. Selection  (3) Nested If else A nested if-else statement is a conditional structure where one if or else block contains another if-else statement. This allows for more complex decision-making by testing multiple conditions in a hierarchical manner.

125. if (condition1) { // Code block if condition1 is true if (condition2) { // Code block if condition2 is true } else { // Code block if condition2 is false } } else { // Code block if condition1 is false } Selection  (3) Nested If else

126. Selection  ( 4 ) Switch if- else Types of selection structure nested if- else switch if-else-i f

127. Selection  ( 4 ) Switch Switch case statements are to check several possible constant values for an expression. Switch form: switch (expression) { case constant1: group of statements1 break case constant2: group of statements2 break . . . default: default group of statements }

128. Selection  ( 4 ) Switch switch evaluates expression and checks if it is equivalent to constant1 , if it is, it executes group of statements1 until it finds the break statement.

129. Selection  ( 4 ) Switch If expression was not equal to constant1 it will be checked against constant2 . If it is equal to this, it will execute statements2.

130. Selection  ( 4 ) Switch If the value of expression DID NOT match any of the previously specified constants (you can include as many case labels as values you want to check), the program will execute the statements included after the default .

131. Selection - switch switch Flow chart

132. Selection  (4) Switch Example 1: x 1 2 Other value Print X is 1 X is 2 Value of x unknown

133. Selection  (4) Switch IPO Analysis : Input: x Process: switch (x) { case 1: print "x is 1“ break case 2: print "x is 2“ break default: Print "value of x unknown” } Output: "x is 1" or "x is 2" or "value of x unknown”

134. Selection  (4) Switch Pseudocode start read x switch (x) { case 1: print "x is 1“ break case 2: print "x is 2" break default: print "value of x unknown” } end

135. b) Flow chart iv) Selection - switch

136. SUMMARY if- else Types of selection structure nested if- switch else * Use an appropriate selection control structure in problem solving

137. Approach in Problem Solving 1.2 Control Structure 1.2.3 Looping

138. SEQUENC E Control Structures SELECTION LOOPING

139. Learning Outcome At the end of this topic, students should be able to: explain the purpose of looping control structure. apply looping control structure in problem solving.

140. What is looping control structure? The looping (or repetition) structure allows a sequence of instructions to be executed repeatedly until a certain condition is reached. The looping structure has three forms: o while o do..while o for

141. The essentials of looping (repetition) The loop counter (loop control variable ): Counts the number of repetitions in the counter- controlled loop Controls the execution of loop The loop counter requires the following to be known in advance: Name of a loop counter Initial value of the loop counter Increment (or decrement ) by which to modify the loop counter in each traversal Condition to test the final value of loop counter

142. The looping control structure: 1. The while Construct

143. The while Construct The while construct has the general form: while (expression) statement; where the expression is first evaluated. If it is true (not zero), the *statement(s) is executed, else if it false (zero), the statement is bypassed. * note : statement(s); which can be a block of statements – more than 1 statement

144. Applying Algorithm in while Construct Pseudocode start initialize counter while (expression) statement(s) counter increment end 1 2 4 3 * note : please refer to slide #4 for numbering details

145. Applying Algorithm in while Construct Flow Chart start initialize counter while (expression) True statement(s) counter increment False end

146. The Counter Table for while Construct counter expression input process output counter increment initial value of counter condition to test IPO analysis increment to modify the loop process output i = i + 1 ample of while counter table: i i <= 3 input

147. Example 1: while Construct Problem Statement: Calculate the area of a rectangle for 3 times. width H eight Remember to plan your algorithm. Do Problem Analysis. Transfer to Pseudocode or Flow Chart.

148. i i <= 3 area i = i + 1 while counter table width,height area = width * height Example 1: while Construct Problem Analysis: Input: width, height Process: area = width * height Output: area

149. i i <= 3 width,height area = width * height area i = i + 1 1 T 2 2 T 3 3 T 4 Loop terminate Example 1: while Construct Problem Analysis: Input: width, height Process: area = width * height Output: area while counter table

150. Pseudocode start initialize counter i = 1 while (i <= 3) input width, height calculate area of rectangle area = width * height print area counter increment i = i + 1 Example 1: while Construct 7. repeat until i > 3 end IPO analysis initial value of counter condition to test increment to modify the loop Repeat step 2 – 6 until expression is false

151. Flow Chart Example 1: while Construct start (i <= 3) True width, height i = i + 1 i = 1 False end area = width * height area

152. The looping control structure: 2. The do..while Construct

153. The do..while Construct The do..while construct has the general form: do statement while (expression); where the expression is last evaluated, after the statement(s) is executed. This means the statement(s) in the do..while will be executed at least once .

154. Applying Algorithm in do..while Construct Pseudocode start initialize counter do statement(s) counter increment while (expression) end 1 2 4 3 * note : please refer to slide #4 for numbering details

155. Applying Algorithm in do..while Construct Flow Chart start True initialize counter statement(s) counter increment while (expression) False end

156. The Counter Table for do..while Construct counter input process output counter increment expression initial value of counter condition to test IPO analysis increment to modify the loop output i = i + 1 i <= 3 ample of do..while counter table: i input process

157. Example 2: do..while Construct Problem Statement: Calculate the area of a rectangle for 3 times. width H eight Remember to plan your algorithm. Do Problem Analysis. Transfer to Pseudocode or Flow Chart.

158. i width,height i = i + 1 i <= 3 do..while counter table area = width * height area Example 2: do..while Construct Problem Analysis: Input: width, height Process: area = width * height Output: area

159. 02/10/12 i width,height area = width * height area i = i + 1 i <= 3 1 2 T 2 3 T 3 4 F Loop terminate Example 2: do..while Construct Problem Analysis: Input: width, height Process: area = width * height Output: area do..while counter table

160. 02/10/12 Pseudocode start Example 2: do..while Construct initialize counter i = 1 do input width, height calculate area of rectangle area = width * height print area counter increment i = i + 1 repeat while (i <= 3) end IPO analysis initial value of counter condition to test increment to modify the loop

161. 02/10 /12 Flow Chart Example 2: do..while Construct start (i <= 3) True False end i = 1 width, height area = width * height area i = i + 1

162. 02/10/12 3. The for Construct The looping control structure:

163. * n o 2 t / e 1 : s / 1 t a 2 t e me n t ( s ); which can be a block of statements – more than 1 statement The for Construct The for construct has the general form: for (initialization; expression; incrementation) statement; where the initialization refers to the initial value of a loop counter. the expression determines whether the loop should be continued; if it is true (not zero), the *statement(s) is executed, else if it false (zero), the for loop is terminated. The incrementation increments the loop counter.

164. * note : please refer to slide #4 for numbering details 02/10/12 Applying Algorithm in for Construct Pseudocode 2 1 4 3 start for (initialize counter; expression; counter increment) statement(s); end

165. start for (initialize counter; expression; counter increment) statement(s); end After one- time initialization, the expression is first evaluated. If it is false , the for loop is terminated; if it is true the statement(s) in the loop is executed. And then the incrementation is performed. The expression condition is again evaluated, until 02 / 1 t h / e 1 2 e x p r e ss io n becomes false. The for loop is executed as follows:

166. Applying Algorithm in for Construct Flow Chart start True statement(s) counter increment initialize counter False (expression) end

167. The Counter Table for for Construct counter expression input process output counter increment initial value of counter condition to test IPO analysis increment to modify the loop process output i = i + 1 ample of for counter table: i i <= 3 input

168. Example 3: for Construct Problem Statement: Calculate the area of a rectangle for 3 times. width height Remember to plan your algorithm. Do Problem Analysis. Transfer to Pseudocode or Flow Chart.

169. i i <= 3 area i = i + 1 for counter table width,height area = width * height Example 3: for Construct Problem Analysis: Input: width, height Process: area = width * height Output: area

170. i i <= 3 width,height area = width * height area i = i + 1 1 T 2 2 T 3 3 T 4 4 F Loop terminate Example 3: for Construct Problem Analysis: Input: width, height Process: area = width * height Output: area for counter table

171. Example 3: for Construct Pseudocode start initialize counter i = 1 for (i <= 3) read width, height calculate area of rectangle area = width * height print area counter increment i = i + 1 7. repeat until i > 3 end IPO analysis initial value of counter condition to test increment to modify the loop Repeat step 3 – 7 until expression is false

172. Flow Chart Example 3: for Construct start (i <= 3) True width, height i = i + 1 i = 1 False end area = width * height area

173. Accumulating in Problem Solving Accumulating or summing is a task a program must often perform. Accumulating means summing a group of numbers : where a variable is added to another variable, which holds the value of the sum or total. The expression for accumulating is as follow: m = m + su su num total = total + marks 2 1 2 1

174. Solving? How to apply Accumulating in Problem Example 4: Accumulating in Sequence Structure Problem Statement: Calculate the average of three numbers. Problem Analysis: Input: num1, num2, num3 Process: total = num1 + num2 + num3 average = total / 3 or average = (num1 + num2 + num3) / 3 Output: average Accumulating

175. How to apply Accumulating in Looping? Example 5: Accumulating in Looping Structure Problem Statement: Calculate the average of three numbers. Problem Analysis: Accumulating Input: num Process: total = total + num average = total / 3 Output: average

176. Example 5: Accumulating in Looping Structure Problem Analysis: Input: num Process: total = total + num average = total / 3 Output: average Using accumulating in while construct ( while counter table) total i i <= 3 num total = total + num i = i + 1 average = total / 3 average 1 T 70 70 2 2 T 80 150 3 3 T 90 240 4 02 /1 / 4 1 2 F Loop terminate average = 240 / 3 80

177. Pseudocode for Accumulating in while initial value of total initial value of counter condition to test IPO analysis increment to modify the loop Repeat step 3 – 6 until expression is false IPO analysis Construct: start initialize total total = initialize counter i = 1 while (i <= 3) input num accumulate total total = total + num counter increment i = i + 1 repeat until i > 3 calculate average average = total / 3 print average end

178. Flow Chart for Accumulating in while Construct: (i <= 3) True num end total = total + num i = i + 1 start total = i = 1 False average = total / 3 average

179. Summary What have you learned? The three forms of looping control structure: while do..while for The loop counter requirement. Apply looping control structure in problem solving. Remember to plan your algorithm. Do Problem Analysis. Transfer to Pseudocode or Flow Chart. Applying accumulating in looping.