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Sunday, 28 August 2016

Chapter 8 Exercise 11, Introduction to Java Programming, Tenth Edition Y. Daniel LiangY.

**8.11 (Game: nine heads and tails) Nine coins are placed in a 3-by-3 matrix with some face up and some face down. You can represent the state of the coins using a 3-by-3 matrix with values 0 (heads) and 1 (tails). Here are some examples:
0 0 0    1 0 1    1 1 0    1 0 1    1 0 0
0 1 0    0 0 1    1 0 0    1 1 0    1 1 1
0 0 0    1 0 0    0 0 1    1 0 0    1 1 0  
Each state can also be represented using a binary number. For example, the preceding matrices correspond to the numbers

000010000 101001100 110100001 101110100 100111110

There are a total of 512 possibilities, so you can use decimal numbers 0, 1, 2, 3, . . . , and 511 to represent all states of the matrix. Write a program that prompts the user to enter a number between 0 and 511 and displays the corresponding matrix with the characters H and T. Here is a sample run: Enter a number between 0 and 511: 7
H H H
H H H
 T T T
 The user entered 7, which corresponds to 000000111. Since 0 stands for H and 1 for T, the output is correct.



import java.util.Scanner;
 
 
public class ProgrammingEx8_11 {
 // Strategies:
 // Use binary number and bitwise operator to shift the bit to the right and
 // use masking to extract the last digit
 // Also see exercise 5.44
 public static void main(String[] args) {
 
  Scanner input = new Scanner(System.in);
  System.out.print("Enter a number between 0 and 511: ");
  short n = input.nextShort();
  int intArray[][] = new int[3][3];
 
  short mask = 0b1; // to extract the last bit after shifting
 
  for (int i = 0; i < 9; i++) {
 
   short bit = (short) (n & mask); // extracting last bit i.e the
           // remainder of
   // division by 2
   intArray[2-i / 3][2-i % 3] = bit;
   n = (byte) (n >> 1); // Shifting right is dividing by 2. The last
         // bit is the remainder of the next shift.
 
  }
 
  displayArray(intArray);
 
 }
 
 public static void displayArray(int array[][]) {
 
  for (int i = 0; i < array.length; i++) {
   for (int j = 0; j < array[0].length; j++) {
    if (array[i][j] == 1) {
     System.out.print("T ");
    } else {
     System.out.print("H ");
    }
   }
 
   System.out.println("");
  }
 }
 
}

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