1. Code Compression the benefits of looping... Today in CS 5 HW 4 - (3 problems) M/T sections W/Th sections due Sunday, 9/26 at midnight due Monday, 9/27 at midnight Reading: Class notes for week 4 Coding style & commenting will count for HW4 ! Let’s Make a Deal Friday, 8:00 am – recitation section Grading and the submission website... concerns? questions? optional, but all are welcome! Lab: N-Z all others welcome!

2. Today in CS 5 Code Compression the benefits of looping... int i = 0; while (i < 4) { ++i; } for (int i=0 ; i<4 ; ++i) { ; } for loop while loop more braces!

3. Style /* * Author: me! * Date: 9/26/04 * Time: d+(int)d/x minutes * Comment: The virtual lyricist */ class CS5App { public static void main(String[] args) { H.pl(“Enter your favorite mascot: ”); String mascot = H.nw(); … more code here … } leave space before blocks of code leave space between parts of code that do different things introductory comment indent code evenly within the surrounding braces align curly braces that correspond use reasonable variable names

4. Comments ? /* * Author: me! * Date: 9/26/04 * Time: 3 kiloseconds * Comment: Finding the max and min of 4 values */ if ( a < b && a < c && a < d ) // see if a is minimal { H.pl(“ Minimum is ” + a); } else if ( b < a && b < c && b < d ) // see if b is minimal { H.pl(“ Minimum is ” + b); } introductory comment comment at least each block of code very small blocks need only one comment for the entire group

5. Back inside the machine... Shortcuts for changing variables: i++;++i; int i = 35; i = i + 1; i += 1;

6. Back inside the machine... Shortcuts for changing variables: i++;++i; int i = 35; i = i + 1; i += 1; all of these increment i by 1

7. Back inside the machine... Shortcuts for changing variables: i++;++i; int i = 35; i = i + 1; i += 1; int amoebas = 100000; amoebas = amoebas * 2; double hwToGo = 11.0; hwToGo = hwToGo - 1; long u235 = 10000000000000L; u235 = u235 / 2; all of these increment i by 1

8. Back inside the machine... Shortcuts for changing variables: i++;++i; int i = 35; i = i + 1; i += 1; int amoebas = 100000; amoebas = amoebas * 2; double hwToGo = 11.0; hwToGo = hwToGo - 1; long u235 = 10000000000000L; u235 = u235 / 2; all of these increment i by 1 amoebas *= 2; hwToGo -= 1;--hwToGo; u235 /= 2;

9. An aside What’s the difference between i++++i and? Nothing -- when they are on their own!

10. An aside What’s the difference between i++++i and? Nothing -- when they are on their own! When they are being used and set at the same time things change... int i = 32; int x = ++i + 10; int i = 32; int x = i++ + 10; increments after useincrements before use

11. An aside What’s the difference between i++++i and? Nothing -- when they are on their own! When they are being used and set at the same time things change... int i = 32; int x = ++i + 10; int i = 32; int x = i++ + 10; increments after useincrements before use i is 33 x is 43 i is 33 x is 42

12. Hw 4, Problem 1 Hw4Pr1) The improved math menu... Option # 2: this integral Option # 4: unlimited max and min Hw4Pr2) Let’s Make a Deal ! Hw4Pr3) Let’s Make A LOT of Deals. Option # 3: function graphing Option # 0: sequences Option # 1: raw power dx x = 0 x =  the period of a pendulum with length L and initial angle a Pair Programming Problem

13. code != work Sequencing items with a single piece of code 7 14 21 28 35 3 6 9 18 21 2 22 222 42 42 42 42 42

14. code != work Sequencing items with a single piece of code 7 14 21 28 35 42 3 6 9 18 21 42 2 22 222 2222 42 42 42

15. Anatomy of a for loop for ( int i = 0 ; i < 4 ; ++i ) { H.pl(i); }

16. Anatomy of a for loop for ( int i = 0 ; i < 4 ; ++i ) { H.pl(i); } PART 1PART 2 PART 3 PART 4

17. Anatomy of a for loop for ( int i = 0 ; i < 4 ; ++i ) { H.pl(i); } PART 1PART 2 PART 1 PART 4 int i 0 PART 2 PART 3 PART 4 create and initialize loop variable PART 3 test to determine if we run the loop loop body is run if test is true update the loop variable always truefalse i<4 end loop

18. code != work Sequencing items with a single piece of code 7 14 21 28 35 42 3 6 9 18 21 42 2 22 222 2222 42 42 42

19. an egocentric for loop for ( int i = 1 ; i <= 6 ; ++i ) { H.p( 7*i ); }

20. a selfless for loop int x = 42; for ( int i = 0 ; i < 6 ; ++i ) { H.p( x + “ ” ); }

21. sharing with if int x = 3; for ( int i = 0 ; i < 6 ; ++i ) { H.p( x + “ ” ); if (x%2 == 0) else }

22. “Quiz” Print the output of these loops A B C int s = 0; for (int i = 1 ; i < 5 ; ++i) { H.p( i + “ ” ); s = s + i; } H.pl(“\ns is ” + s); int c = 0; for (int i=10 ; i>0 ; i/=2 ) { H.p( i + “ ” ); c++; } H.pl(“c is ” + c); for (int i = 0 ; i != 4 ; i+=1) { H.p( i + “ ” ); } “Extra Credit” change one character in the code above so that this loop runs 4294967292 times.

23. “Quiz”, part 2 0 1 2 3 6 7 14 15 30 Write a loop to print this sequence: 9 terms total 2 22 222 2222... 9 terms total Write a loop to print this sequence: Hint: Use a for loop with an if inside it! Hint: Use a for loop with a for loop inside it!

24. Variables: a life story... int sum = 0; for ( int i = 1 ; i < 5 ; ++i ) { sum = sum + i; } H.pl(“sum is ” + sum); int sum = 0; for ( int i = 0 … Why will java complain about this ?!?

25. Variables: a life story... int sum = 0; for ( int i = 1 ; i < 5 ; ++i ) { sum = sum + i; } H.pl(“sum is ” + sum); int sum = 0; for ( int i = 0 … (1) Birth (of sum and i ) Why will java complain about this ?!?

26. Variables: a life story... int sum = 0; for ( int i = 1 ; i < 5 ; ++i ) { sum = sum + i; } H.pl(“sum is ” + sum); int sum = 0; for ( int i = 0 … (1) Birth (of sum and i ) (2) Growth Why will java complain about this ?!?

27. Variables: a life story... int sum = 0; for ( int i = 1 ; i < 5 ; ++i ) { sum = sum + i; } H.pl(“sum is ” + sum); int sum = 0; for ( int i = 0 … (1) Birth (of sum and i ) (2) Growth (3) Death (of i ) but sum lives on… Why will java complain about this ?!?

28. Variables: a life story... int sum = 0; for ( int i = 1 ; i < 5 ; ++i ) { sum = sum + i; } H.pl(“sum is ” + sum); sum = 0; for ( int i = 0 … (1) Birth (of sum and i ) (2) Growth (3) Death (of i ) but sum lives on… reuse is OK recreation is not!

29. What’s this all for ? Program for finding the factorial of a number… H.pl(“Type an integer n and I will print n!”); int n = H.ni(); // we have n – we need n factorial int result = ; // be sure to give an initial value H.pl(“The result is ” + result); Use the same idea for creating powers in Hw4 Pr1 !

30. Perspective on for loops // Name: CS5App // Author: Matt Beaumont // Purpose: To get me out of CS5... //...no, really... // Purpose: To create and maintain a list // of films and directors /* Notes: * I haven't liked for-loops since the day I met them. * They bother me for some reason. Hence, no for-loops… */ class CS5App {... At the top of a CS 5 placement project file …

31. Extreme Looping Java’s last and least built-in variable type: boolean H.pl(“It keeps on”); while ( true ) { H.pl(“going and”); } “while” block

32. Extreme Looping Java’s last and least built-in variable type: boolean H.pl(“It keeps on”); while ( true ) { H.pl(“going and”); } “while” block note what’s NOT here!

33. Extreme Looping with while No variable or expression is needed! H.pl(“It keeps on”); while ( true ) { H.pl(“going and”); int escape = H.randInt(1,100); if (escape == 100) { break; } worry later about how to escape ! here is how to quit – use break !

34. “User – friendly” code long myNumber = H.randLong(0,9000000000000000000L); while ( true ) { H.pl(“I’m thinking of a positive integer”); H.pl(“If you guess it, you may leave.”); H.pl(“Otherwise, you must continue…\n”); H.p(“What is your guess? ”); int yourGuess = H.ni(); if ( yourGuess == myNumber ) { break; // let me out ! } A break breaks out of the enclosing switch, for, or while.

35. “User – friendly” code long myNumber = H.randLong(0,9000000000000000000L); while ( true ) { H.pl(“I’m thinking of a positive integer”); H.pl(“If you guess it, you may leave.”); H.pl(“Otherwise, you must continue…\n”); H.p(“What is your guess? ”); int yourGuess = H.ni(); if ( yourGuess == myNumber ) break; // let me out ! H.p(“Would you like to continue playing? ”); String answer = H.nl(); if (answer == “no”) break; } but friendlier! same as before

36. Monty Hall Let’s make a deal ’63-’86 Sept. 1990 inspiring the “Monty Hall paradox” Hw4Pr2) The Virtual Monty Hall

37. The two Monte Carlos Monte Carlo casino, Monaco Making random numbers work for you! Monte Carlo methods, Math/CS math hw cs hw physics hw Hum hw

38. Monte Carlo Monty Hall Suppose you always switch to the other door... What are the chances that you will win the car ? Hw4Pr3) Monte Carlo Monty Hall Run it (randomly) 1000 times and see!

39. Monty Hall program design top-down software engineering while (true) // program skeleton via short comments { } HW4PR3) Virtual Monty Hall Detailed design this Friday in recitation…

40. Monte Carlo in action Suppose you roll two dice. What are the chances that you roll doubles? int doublesCount = 0; for (int i=0 ; i<1000 ; ++i) { int d1 = H.randInt(1,6); int d2 = H.randInt(1,6); if ( d1 == d2 ) { ++doublesCount; } H.pl(“We rolled ” + doublesCount + “ doubles.”); one roll of the dice 1000 times count the number of doubles rolled set up a variable to count the number of doubles rolled

41. Summary for loop examples while loop examples statements and shortcuts for changing variables for (int i=12 ; i>=0 ; i-=2) { H.p( i + “ ” ); } int x = 3; for (int i=0 ; i<9 ; ++i) { H.p( x + “ ” ); x = x + 12; } x *= 10; num += 10; while ( true ) { String s = H.nw(); if (s.equals(“no”)) break; } ++i; i++;--i; i--; multiply x by 10increase num by 10increase i by 1decrease i by 1 prints 12 10 8 6 4 2 0 prints 3 15 27 39 51 63 75 87 99 continues until the user types “no”

42. Lab Today I’d suggest starting by writing the for loops in Hw4Pr1 then move on to the more involved examples... 10 15 20 25 30 35 40 45 50 55 60 65 11 22 33 44 55 66 77 88 99 110 121 1 2 4 8 16 32 64 128 256 512 1024 2048 0 3 9 12 36 39 117 120 360 363 1089 1 22 333 4444 55555 666666 7777777 88888888 use loops to print these sequences Hw4Pr2 Hw4Pr3Monte Carlo Monty Hall ( for ) Virtual Monty Hall ( while ) print the sum of the first four sequences, too … N-Z all others welcome! Hw4Pr1) Improved Math MenuPair Programming Problem

43. Summary for loop examples while loop examples statements and shortcuts for changing variables for (int i=12 ; i>=0 ; i-=2) { H.p( i + “ ” ); } int x = 3; for (int i=0 ; i<9 ; ++i) { H.p( x + “ ” ); x = x + 12; } x *= 10; num += 10; while ( true ) { String s = H.nw(); if (s.equals(“no”)) break; } ++i; i++;--i; i--; multiply x by 10increase num by 10increase i by 1decrease i by 1 prints 12 10 8 6 4 2 0 prints 3 15 27 39 51 63 75 87 99 continues until the user types “no”

44. “Quiz” Print the output of these loops: Names: A B C int s = 0; for (int x = 1 ; x < 5 ; ++x) { H.p( x + “ ” ); s = s + x; } H.pl(“\ns is ” + s); int i = 20; while (i > 0) { i /= 2; H.p( i + “ ” ); } for (int i = 10 ; i > 0 ; i+=1 ) { H.p( i + “ ” ); }

45. “Quiz”, part 2 0 1 2 3 6 7 14 15 30 Write a loop to print this sequence: 9 terms total 0 00 000 0000... 9 terms total Write a loop to print this sequence: Hint: Use a for loop with an if inside it! Hint: Use a for loop with a for loop inside it!

46. A C int s = 0; for (int x = 1 ; x < 5 ; ++x) { H.p( x + “ ” ); s = s + x; } H.pl(“\ns is ” + s); int i = 20; while (i > 0) { i /= 2; H.p( i + “ ” ); } for (int i = 10 ; i > 0 ; i = i-2) { H.p( i + “ ” ); } prints B

47. int s = 0; for (int x = 1 ; x < 5 ; ++x) { H.p( x + “ ” ); s = s + x; } H.pl(“\ns is ” + s); int i = 20; while (i > 0) { i /= 2; H.p( i + “ ” ); } for (int i = 10 ; i > 0 ; i = i-2) { H.p( i + “ ” ); } 10 8 6 4 2 prints A C B

48. int s = 0; for (int x = 1 ; x < 5 ; ++x) { H.p( x + “ ” ); s = s + x; } H.pl(“\ns is ” + s); int i = 20; while (i > 0) { i /= 2; H.p( i + “ ” ); } for (int i = 10 ; i > 0 ; i = i-2) { H.p( i + “ ” ); } 10 8 6 4 2 10 5 2 1 0 prints

49. int s = 0; for (int x = 1 ; x < 5 ; ++x) { H.p( x + “ ” ); s = s + x; } H.pl(“\ns is ” + s); int i = 20; while (i > 0) { i /= 2; H.p( i + “ ” ); } for (int i = 10 ; i > 0 ; i = i-2) { H.p( i + “ ” ); } 10 8 6 4 2 10 5 2 1 0 prints 1 2 3 4 s is 10 A C B

50. 0 1 2 3 6 7 14 15 30 Write a loop to print this sequence: 9 terms total int x = 0; for (int i=0 ; i<9 ; ++i) { H.p( x + “ ” ); if ( i%2 == 0 ) { x = x + 1; } else { x = x * 2; } i = 0 i = 1 i = 2 i = 3 i = 4 i = 5 i = 6 i = 7 i = 8 shorter?

51. 0 1 2 3 6 7 14 15 30 Write a loop to print this sequence: 9 terms total int x = 0; for (int i=0 ; i<9 ; ++i) { H.p( x + “ ” ); if ( i%2 == 0 ) ++x; else x *= 2; } i = 0 i = 1 i = 2 i = 3 i = 4 i = 5 i = 6 i = 7 i = 8 ifs and elses have one-line bodies (“blocks”) if no curly braces are used

52. 0 00 000 0000... Write a loop to print this sequence: 9 terms total for (int i=1 ; i<10 ; ++i) { for (int j=1 ; j<=i ; ++j) { H.p(0); } H.p(“ ”); } i = 1 i = 2 i = 3 i = 4 j = 1 j = 3 j = 1 j = 2 j = 1 j = 2 j = 3j = 1 j = 2j = 4 shorter?

53. 0 00 000 0000... Write a loop to print this sequence: 9 terms total for (int i=1 ; i<10 ; ++i) { for (int j=1 ; j<=i ; ++j) H.p(0); H.p(“ ”); } i = 1 i = 2 i = 3 i = 4 j = 1 j = 3 j = 1 j = 2 j = 1 j = 2 j = 3j = 1 j = 2j = 4 ifs and elses have one-line bodies (“blocks”) if no curly braces are used

54. Variables: a life story... int sum = 0; for ( int x = 0 ; x < 6 ; ++x ) { H.p( x + “ ” ); sum = sum + x; } H.pl(“sum is ” + sum); (1) Birth (of sum and x )

55. Variables: a life story... int sum = 0; for ( int x = 0 ; x < 6 ; ++x ) { H.p( x + “ ” ); sum = sum + x; } H.pl(“sum is ” + sum); (1) Birth (of sum and x ) (2) Growth

56. Variables: a life story... int sum = 0; for ( int x = 0 ; x < 6 ; ++x ) { H.p( x + “ ” ); sum = sum + x; } H.pl(“sum is ” + sum); A variable’s scope is the block of code in which it is declared. (1) Birth (of sum and x ) A variable only exists until the closing curly brace of its scope... (2) Growth (3) Death (of x )

57. Variables: a life story... int sum = 0; for ( int x = 0 ; x < 6 ; ++x ) { H.p( x + “ ” ); sum = sum + x; } H.pl(“sum is ” + sum); int sum = 0; for … next loop here … (1) Birth (of sum and x ) (2) Growth (3) Death (of x ) Why will java complain about this ?!?

58. Variables: a life story... int sum = 0; for ( int x = 0 ; x < 6 ; ++x ) { H.p( x + “ ” ); sum = sum + x; } H.pl(“sum is ” + sum); sum = 0; for … next loop here … (1) Birth (of sum and x ) (2) Growth (3) Death (of x ) You can reuse But you can’t redeclare !

59. What’s this all for ? Program for factorial input: an integer n output: the integer n! case 1: { H.pl(“Type an integer n and I will print n!”); int n = H.ni(); // we have n – we need n! } Use the same idea for creating powers !

60. Extreme Looping with while No variable or expression is needed! H.pl(“It keeps on”); while ( true ) { H.pl(“going and”); } worry later about how to escape !

61. Extreme Looping with while No variable or expression is needed! H.pl(“It keeps on”); while ( true ) { H.pl(“going and”); int escape = H.randInt(1,100); if (escape == 100) { break; } worry later about how to escape ! here is how to quit – use break !

62. “User – friendly” code long myNumber = H.randLong(0,9000000000000000000L); while ( true ) { H.pl(“I’m thinking of a positive integer”); H.pl(“If you guess it, you may leave.”); H.pl(“Otherwise, you must continue…\n”); H.p(“What is your guess? ”); int yourGuess = H.ni(); if ( yourGuess == myNumber ) { break; // let me out ! } A break breaks out of the enclosing switch, for, or while.

63. “User – friendly” code long myNumber = H.randLong(0,9000000000000000000L); while ( true ) { H.pl(“I’m thinking of a positive integer”); H.pl(“If you guess it, you may leave.”); H.pl(“Otherwise, you must continue…\n”); H.p(“What is your guess? ”); int yourGuess = H.ni(); if ( yourGuess == myNumber ) { break; // let me out ! } H.p(“Would you like to continue playing? ”); String answer = H.nl(); if (answer == “no”) break; } much friendlier! same as before

64. Monty Hall Let’s make a deal ’63-’86 Sept. 1990 inspiring the “Monty Hall paradox”

65. Monte Carlo Monty Hall Suppose you always switch to the other door... What are the chances that you will win the car ? Hw4Pr3) Monte Carlo Monty Hall Run it (randomly) 1000 times and see!

66. The two Monte Carlos Monte Carlo casino, Monaco Making random numbers work for you! Monte Carlo methods, Math/CS math hw cs hw physics hw Hum hw

67. Summary for loop examples while loop examples statements and shortcuts for changing variables for (int i=12 ; i>=0 ; i-=2) { H.p( i + “ ” ); } int x = 3; for (int i=0 ; i<9 ; ++i) { H.p( x + “ ” ); x = x + 12; } x *= 10; num += 10; while ( true ) { String s = H.nw(); if (s.equals(“no”)) break; } ++i; i++;--i; i--; multiply x by 10increase num by 10increase i by 1decrease i by 1 prints 12 10 8 6 4 2 0 prints 3 15 27 39 51 63 75 87 99 continues until the user types “no”

68. Hw4, Pr1, Option 2: integration!

69. Prof. Jacobsen goes hungry...

70. Monte Carlo in action Suppose you roll two dice. What are the chances that you roll doubles? int doublesCount = 0; for (int i=0 ; i<1000 ; ++i) { int d1 = H.randInt(1,6); int d2 = H.randInt(1,6); if ( d1 == d2 ) { ++doublesCount; } H.pl(“We rolled ” + doublesCount + “ doubles.”); one roll of the dice 1000 times count the number of doubles rolled set up a variable to count the number of doubles rolled

71. Lab Today I’d suggest starting by writing the for loops in Hw4Pr1 then move on to the more involved examples... 10 15 20 25 30 35 40 45 50 55 60 65 11 22 33 44 55 66 77 88 99 110 121 1 2 4 8 16 32 64 128 256 512 1024 2048 0 3 9 12 36 39 117 120 360 363 1089 1 22 333 4444 55555 666666 7777777 88888888 use loops to print these sequences Hw4Pr2 Hw4Pr3Monte Carlo Monty Hall ( for ) Virtual Monty Hall ( while ) print the sum of just the first four sequences, too … N-Z and any others…

72. Hw4, Pr1, Option 4: random sums See the Improved Moth Menu for working example code at www.cs.hmc.edu/~dodds/cs5 case 4: { Histogram h = new Histogram(); for (int i=0 ; i<50000 ; ++i) h.addPoint(Math.random()); outerFrame.updateSize(); break; } Your task: plot sums of random numbers min x is ~0 max x is ~1 current plot: 50000 random numberscurrent code: 50000 random numbers

73. Variables: a life story... for ( int i = 0 ; i < 6 ; ++i ) { int x = 1; H.out.print( x + “ ” ); x = x*3; } A variable’s scope is the block of code in which it is declared. (1) Birth (of x and i ) (2) Growth (3) Death A variable only exists until the closing curly brace of its scope...

74. A variable’s scope is the block of code in which it is declared. (1) Birth (of x and i ) (3) Death A variable only exists until the closing curly brace of its scope...

75. A variable’s scope is the block of code in which it is declared. (2) Growth (3) Death A variable only exists until the closing curly brace of its scope...

76. Variables: a life story... for ( int i = 0 ; i < 6 ; ++i ) { int x = 1; H.out.print( x + “ ” ); x = x*3; } A variable’s scope is the block of code in which it is declared. (1) Birth (of x and i ) (2) Growth (3) Death A variable only exists until the closing curly brace of its scope...

77. Variables: a life story... for ( int i = 0 ; i < 6 ; ++i ) { int x = 1; H.out.print( x + “ ” ); x = x*3; } A variable’s scope is the block of code in which it is declared. (1) Birth (of x and i ) (2) Growth (3) Death A variable only exists until the closing curly brace of its scope...

78. Back inside the machine... Shortcuts for changing variables: i++;++i; int i = 33; i = i + 1; i += 1;

79. int amoebas = 100000; amoebas = amoebas * 2; double hwToGo = 11.0; hwToGo = hwToGo - 1; long u235 = 10000000000000L; u235 = u235 / 2;

80. Program design top-down software engineering in general: start with program skeleton boolean done = false; while ( !done ) { add details to structure compile && run program if ( everything == OK ) done = true; }

81. Anatomy of a for loop for ( int i = 0 ; i < 9 ; ++i ) { H.out.println(“i is ” + i); } the “for” block #0 - create and initialize loop variables #1 - check the test condition #2 - execute all of the code in the “for” block #3 - update loop variables as desired; goto #1 if false, stop looping & jump past the “for” block if true, continue looping initialization statement test variable updates 0 1 2 3

82. Anatomy of a for loop for ( int i = 0 ; i < 9 ; ++i ) { H.out.println(“i is ” + i); } #0 - create and initialize loop variables initialization statement int i 0

83. Anatomy of a for loop for ( int i = 0 ; i < 9 ; ++i ) { H.out.println(“i is ” + i); } #0 - create and initialize loop variables #1 - check the test condition if false, stop looping & jump past the “for” block if true, continue looping test int i 0

84. Anatomy of a for loop for ( int i = 0 ; i < 9 ; ++i ) { H.out.println(“i is ” + i); } #0 - create and initialize loop variables #1 - check the test condition #2 - execute all of the code in the “for” block if false, stop looping & jump past the “for” block if true, continue looping the “for” block i is 0 int i 0 output

85. Anatomy of a for loop for ( int i = 0 ; i < 9 ; ++i ) { H.out.println(“i is ” + i); } #0 - create and initialize loop variables #1 - check the test condition #2 - execute all of the code in the “for” block #3 - update loop variables as desired; goto #1 if false, stop looping & jump past the “for” block if true, continue looping variable updates i is 0 output int i 1

86. Execution of a for loop for ( int i = 0 ; i < 9 ; ++i ) { H.out.println(“i is ” + i); } output:

87. Execution of a for loop for ( int i = 0 ; i < 9 ; ++i ) { H.out.println(“i is ” + i); } i is 0 output: start continue looping if true int i 0 1 before after

88. continue looping if true Execution of a for loop for ( int i = 0 ; i < 9 ; ++i ) { H.out.println(“i is ” + i); } i is 0 i is 1 output: start int i 1 2 before after

89. continue looping if true Execution of a for loop for ( int i = 0 ; i < 9 ; ++i ) { H.out.println(“i is ” + i); } i is 0 i is 1 i is 2 output: start int i 2 3 before after

90. Execution of a for loop for ( int i = 0 ; i < 9 ; ++i ) { H.out.println(“i is ” + i); } i is 0 i is 1 i is 2 … i is 8 output: start int i 8 9 before after continue looping if true

91. Execution of a for loop for ( int i = 0 ; i < 9 ; ++i ) { H.out.println(“i is ” + i); } i is 0 i is 1 i is 2 … i is 8 output: start int i 8 9 before after jump to end of for loop if false continue looping if true

92. Monty Hall Let’s make a deal ’63-’86 Sept. 1990 inspiring the “Monty Hall paradox”

93. Monte Carlo Monte Carlo casino, Monaco Estimating a value (usually a probability) by playing an appropriate game over and over. Monte Carlo methods, Math/CS

94. “Quiz” Print the output of these loops: Names: A B C int s = 0; for (int x = 1 ; x < 5 ; ++x) { H.p( x + “ ” ); s = s + x; } H.pl(“\ns is ” + s); int i = 20; while (i > 0) { i /= 2; H.p( i + “ ” ); } for (int i = 10 ; i > 0 ; i = i-2) { H.p( i + “ ” ); }

95. “Quiz”, part 2 0 1 2 3 6 7 14 15 30 Write a loop to print this sequence: 9 terms total 0 00 000 0000... 9 terms total Write a loop to print this sequence: Hint: Use a for loop with an if inside it! Hint: Use a for loop with a for loop inside it!

96. “Quiz”, part 2 0 1 2 3 6 7 14 15 30 What code (using for ) will print 9 terms total Hw4Pr1) Option #1: sequences 0 1 2 3 6 7 14 15 30

97. Mixing it up... Hw4Pr1) Option #1: sequences 0 00 000 0000… What code (using for ) will print 9 terms total

98. User - friendly code boolean playAgain = true; long mynumber = (long)(Math.random()*9000000000000000000L); while ( playAgain ) { H.pl(“I’m thinking of a positive integer”); H.pl(“If you guess it, you may leave.”); H.pl(“Otherwise, you must continue…\n”); H.p(“What is your guess? ”); int yourguess = H.ni(); if ( yourguess == mynumber ) { playAgain = false; // let me out ! }

99. Variables: a life story... for ( int i = 0 ; i < 6 ; ++i ) { int x = 1; H.p( x + “ ” ); x = x*3; }

100. Variables: a life story... for ( int i = 0 ; i < 6 ; ++i ) { int x = 1; H.p( x + “ ” ); x = x*3; } A variable’s scope is the block of code in which it is declared. (1) Birth (of x and i ) (2) Growth A variable only exists until the closing curly brace of its scope...

101. Variables: a life story... for ( int i = 0 ; i < 6 ; ++i ) { int x = 1; H.p( x + “ ” ); x = x*3; } A variable’s scope is the block of code in which it is declared. (1) Birth (of x and i ) (2) Growth (3) Death A variable only exists until the closing curly brace of its scope...

102. Monty Hall program design top-down software engineering HW4PR3) Virtual Monty Hall write program skeleton while ( true ) { add more details compile && run program if ( everything == OK ) break; } H.pl(“Time to work on Chem...”);

103. 0 00 000 0000... Write a loop to print this sequence: 9 terms total for (int i=1 ; i<10 ; ++i) { for (int j=1 ; j<=i ; ++j) { H.p(0); } H.p(“ ”); } i = 1 i = 2 i = 3 i = 4 j = 1 j = 3 j = 1 j = 2 j = 1 j = 2 j = 3j = 1 j = 2j = 4 shorter?

104. Variables: a life story... int sum = 0; for ( int x = 0 ; x < 6 ; ++x ) { H.p( x + “ ” ); sum = sum + x; } H.pl(“sum is ” + sum); A variable’s scope is the block of code in which it is declared. (1) Birth (of sum and x ) A variable only exists until the closing curly brace of its scope... (2) Growth (3) Death (of x )

105. Variables: a life story... int sum = 0; for ( int x = 0 ; x < 6 ; ++x ) { H.p( x + “ ” ); sum = sum + x; } H.pl(“sum is ” + sum); sum = 0; for … next loop here … (1) Birth (of sum and x ) (2) Growth (3) Death (of x ) You can reuse But you can’t redeclare !

106. What’s this all for ? Program for factorial input: an integer n output: the integer n! case 1: { H.pl(“Type an integer n and I will print n!”); int n = H.ni(); // we have n – we need n! } Use the same idea for creating powers !

107. Extreme Looping with while No variable or expression is needed! H.pl(“It keeps on”); while ( true ) { H.pl(“going and”); double r = Math.random(); if (r > 0.99) { break; } worry later about how to escape ! here is how to quit – use break !

108. “User – friendly” code long myNumber = (long)(Math.random()*9000000000000000000L); while ( true ) { H.pl(“I’m thinking of a positive integer”); H.pl(“If you guess it, you may leave.”); H.pl(“Otherwise, you must continue…\n”); H.p(“What is your guess? ”); int yourGuess = H.ni(); if ( yourGuess == myNumber ) { break; // let me out ! } A break breaks out of the enclosing switch, for, or while.