Simplex locks are keyless locks that have a sequence of buttons. You press the proper combination...

  
 

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Simplex locks are keyless locks that have a sequence of buttons. You press the proper combination of buttons, 12. and the lock opens. A typical lock has five buttons. A combination might be set to three buttons, and then you need to press them in the same order. You never press the same button twice. ... For example the lock for the restroom at the Rob Hill campground in the San Francisco Presidio is opened by the combination 425, as I figured out by trial and error. (They probably changed it by the time you read this.) It is also possible to define combinations with four or five buttons. Is that more secure? Would it be much better to have six buttons? That is what this exercise is about. If the lock has n buttons, and the combination requires k buttons to be pressed, how many combinations are there? Let's call that number combinations (n, k). If k is 1, then you push one button out of n, so combinations (n, 1) is clearly n. If k is greater than one, let us focus on the first button. There are n choices for the first button, and for each of them we get to pick k - 1 choices out of n - 1 buttons. That's the same problem again, with simpler inputs. Complete the method that yields the total number of combinations for a lock with n buttons, of which k are to be selected. SimplexLock.java 1 public class SimplexLocks 2 { 3 4 6 7 8 9 10 11 12 13 123456 14 15 16 17 18 19 20 21 344828 25 26 27 // calculate the factorial int fact(int num) { } // test the function 22 public static void main (String[] args) { 28 } int f=1; for(int i=1;i<=num; i++) f*=i; return f; public int combinations (int n, int k) { } // so, we have result = (n)/ ( (k!)*(n-k)! ) int numerator = fact(n); int denominator = return numerator/denominator; fact(k)* fact (n-k); System.out.println("Combinations (10,4) is "+new SimplexLocks ().combinations (1 System.out.println("Combinations (6,4) is "+new SimplexLocks (). combinations (6, System.out.println("Combinations (10,2) is "+new SimplexLocks (). combinations (1 ... 5. Complete the printCalendarmethod that prints a calendar such as 1 2 3 4 7 8 9 10 5 6 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 The column of the first day and the number of days are given as parameters. The method prints the calendar and returns no result. Calendar.java 1 import java.util.Scanner; 2 3 public class Calender { 456789 7 9 10 11 12 13 System.out.print("Number of days :"); 14 int days=sc. nextInt(); 1 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 15 System.out.print ("Weekday of first day (0 = Sunday) :"); 16 int weekday=sc.nextInt (); 44 45 public static void main (String[] args) { 46 47 48 49 50 51 52 53 53 } * Creating an Scanner class object which is used to get the inputs * entered by the user */ Scanner sc = new Scanner (System.in); System.out.println(" Su Mo Tu We th Fr Sa"); print Calender (weekday, days); } //Getting the input entered by the user } private static void printCalender (int firstDay, int days) { int i; //System.out.println(" "); == if ((firstDay % 7) >= 0) { if ((firstDay % 7) 0) { } else if ((firstDay % 7) System.out.print(" "); } else if ((firstDay % 7) System.out.print ("\t"); } else if ((firstDay % 7) System.out.print("\t\t "); } else if ((firstDay % 7) System.out.print ("\t "); } else if ((firstDay % 7) System.out.print("\t\t "); } else if ((firstDay % 7) System.out.print("\t\t "); } } == } == 2) { == == == 1) { == 3) { 4) { 5) { 6) { for (i = 1; i <= days ; i++) { System.out.printf("%2d " i); if (((i+firstDay) % 7 System.out.println(); 0) || (i == days)) ... 9. In the preceding exercises, you saw how one can use stepwise refinement to solve the problem of translating Wiki markup to HTML. Now turn the pseudocode into code. Complete the convertToHTML and nextSymbol methods in the following class. WikiMarkup.java 1 import java.util.Scanner; 2345678 3 public class WikiMarkup 4 { 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 -10 15 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 } 70 71 70 71 } public static void main(String[] args) { } /** Scanner in = new Scanner (System.in); String message = in.nextLine(); System.out.println(convertToHTML (message)); */ public static String convertToHTML (String message) { String result = message; return result. replace("\\", ""); Converts a message with Wiki markup to HTML. @param message the message with markup @return the message with Wiki notation converted to HTML } /** } /** */ public static int next Symbol (String message, String symbols, int start) { } /** Gets the HTML tag for a markup symbol. @param symbol the markup symbol @return the corresponding HTML tag, or null if none found Finds the next unescaped symbol. @param message a message with Wiki markup @param symbols the symbols to search for @param start the starting position for the search @return the position of the next markup symbol at or after start */ public static String tagForSymbol (char symbol) { } == if (symbol '!') { return "em"; } else if (symbol == else if (symbol else if (symbol else if (symbol == else { return null; } Replaces a character of a string at a given position. @param str the string where the replacement takes place @param position the position of the character to be replaced @param replacement the replacement string, or the original string if position was not valid. */ public static String replaceAt (String str, int position, String replacement) == { if (0<= position && position < str.length()) { ¹*') { return "strong"; } ¹) { return "code"; } ^') { return "super"; } _') { return "sub"; } } else { } return str.substring(0, position) + replacement + str.substring (position + 1); return str; Simplex locks are keyless locks that have a sequence of buttons. You press the proper combination of buttons, 12. and the lock opens. A typical lock has five buttons. A combination might be set to three buttons, and then you need to press them in the same order. You never press the same button twice. ... For example the lock for the restroom at the Rob Hill campground in the San Francisco Presidio is opened by the combination 425, as I figured out by trial and error. (They probably changed it by the time you read this.) It is also possible to define combinations with four or five buttons. Is that more secure? Would it be much better to have six buttons? That is what this exercise is about. If the lock has n buttons, and the combination requires k buttons to be pressed, how many combinations are there? Let's call that number combinations (n, k). If k is 1, then you push one button out of n, so combinations (n, 1) is clearly n. If k is greater than one, let us focus on the first button. There are n choices for the first button, and for each of them we get to pick k - 1 choices out of n - 1 buttons. That's the same problem again, with simpler inputs. Complete the method that yields the total number of combinations for a lock with n buttons, of which k are to be selected. SimplexLock.java 1 public class SimplexLocks 2 { 3 4 6 7 8 9 10 11 12 13 123456 14 15 16 17 18 19 20 21 344828 25 26 27 // calculate the factorial int fact(int num) { } // test the function 22 public static void main (String[] args) { 28 } int f=1; for(int i=1;i<=num; i++) f*=i; return f; public int combinations (int n, int k) { } // so, we have result = (n)/ ( (k!)*(n-k)! ) int numerator = fact(n); int denominator = return numerator/denominator; fact(k)* fact (n-k); System.out.println("Combinations (10,4) is "+new SimplexLocks ().combinations (1 System.out.println("Combinations (6,4) is "+new SimplexLocks (). combinations (6, System.out.println("Combinations (10,2) is "+new SimplexLocks (). combinations (1 ... 5. Complete the printCalendarmethod that prints a calendar such as 1 2 3 4 7 8 9 10 5 6 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 The column of the first day and the number of days are given as parameters. The method prints the calendar and returns no result. Calendar.java 1 import java.util.Scanner; 2 3 public class Calender { 456789 7 9 10 11 12 13 System.out.print("Number of days :"); 14 int days=sc. nextInt(); 1 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 15 System.out.print ("Weekday of first day (0 = Sunday) :"); 16 int weekday=sc.nextInt (); 44 45 public static void main (String[] args) { 46 47 48 49 50 51 52 53 53 } * Creating an Scanner class object which is used to get the inputs * entered by the user */ Scanner sc = new Scanner (System.in); System.out.println(" Su Mo Tu We th Fr Sa"); print Calender (weekday, days); } //Getting the input entered by the user } private static void printCalender (int firstDay, int days) { int i; //System.out.println(" "); == if ((firstDay % 7) >= 0) { if ((firstDay % 7) 0) { } else if ((firstDay % 7) System.out.print(" "); } else if ((firstDay % 7) System.out.print ("\t"); } else if ((firstDay % 7) System.out.print("\t\t "); } else if ((firstDay % 7) System.out.print ("\t "); } else if ((firstDay % 7) System.out.print("\t\t "); } else if ((firstDay % 7) System.out.print("\t\t "); } } == } == 2) { == == == 1) { == 3) { 4) { 5) { 6) { for (i = 1; i <= days ; i++) { System.out.printf("%2d " i); if (((i+firstDay) % 7 System.out.println(); 0) || (i == days)) ... 9. In the preceding exercises, you saw how one can use stepwise refinement to solve the problem of translating Wiki markup to HTML. Now turn the pseudocode into code. Complete the convertToHTML and nextSymbol methods in the following class. WikiMarkup.java 1 import java.util.Scanner; 2345678 3 public class WikiMarkup 4 { 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 -10 15 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 } 70 71 70 71 } public static void main(String[] args) { } /** Scanner in = new Scanner (System.in); String message = in.nextLine(); System.out.println(convertToHTML (message)); */ public static String convertToHTML (String message) { String result = message; return result. replace("\\", ""); Converts a message with Wiki markup to HTML. @param message the message with markup @return the message with Wiki notation converted to HTML } /** } /** */ public static int next Symbol (String message, String symbols, int start) { } /** Gets the HTML tag for a markup symbol. @param symbol the markup symbol @return the corresponding HTML tag, or null if none found Finds the next unescaped symbol. @param message a message with Wiki markup @param symbols the symbols to search for @param start the starting position for the search @return the position of the next markup symbol at or after start */ public static String tagForSymbol (char symbol) { } == if (symbol '!') { return "em"; } else if (symbol == else if (symbol else if (symbol else if (symbol == else { return null; } Replaces a character of a string at a given position. @param str the string where the replacement takes place @param position the position of the character to be replaced @param replacement the replacement string, or the original string if position was not valid. */ public static String replaceAt (String str, int position, String replacement) == { if (0<= position && position < str.length()) { ¹*') { return "strong"; } ¹) { return "code"; } ^') { return "super"; } _') { return "sub"; } } else { } return str.substring(0, position) + replacement + str.substring (position + 1); return str;

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