27 Nov 06

present: ic, nj, mm, kt, sw, ip


I. New statements learnt this week:

   a) define an array of certain type:
           one -dimensional:
           <type> [] <name of array> = new <type> [<max index>]
           
           two - dimensional: 
           <type> [][] <name of array> = new <type> [<max row index>][<max colume index>]

   b) array element i:

           A[i], A[5], A[6] etc.

   c) Examples of an array:  What is an array?  What is an one-dimonsional array?

           i) an array of integers:

                   index  0  1 2 3  4 5
                   A      23 2 1 10 6 4

           ii) an array of char:
           (chars should be quoted by `', e.g. `a')

                   index  0 1 2 3 4 5
                   A      a b c d e f

II. Problems:

        1) define an integer array A up to 100 indices:

           int [] A = new int [100];

        2) points to the 3rd and 5th elements in example c)ii):

           A[2], A[4]

        3) display element i:

           System.out.println(A[i]);

        4) display all the elements in A[0..8]:

           for (int i=0; i<9; i++) {
              System.out.println(A[i]);
           }

        5) display all the elements in reverse order:

           for (int i=8; i>=0; i--) {
              System.out.println(A[i]);
           }


        6) compute and display the total of the elements A[3--8]:

           int total = 0;
           for (int i=3; i<9; i++) {
              total = total+A[i];
              System.out.println(A[i]);
           }
           System.out.println(total);

        7) input 10 integers from the keyboard, and store them in
        array A:

           import java.util.Scanner;

           Scanner keyboard = new Scanner(System.in);

           for (int i=0; i<10; i++) {
              A[i] = keyboard.nextInt();
           }
           for (int i=0; i<10; i++) {
              System.out.println(A[i]);
           }

        8) store 10 random integers ranging [2,5] in an array A, and display them.

	   import java.util.Random;
	   
	   Random r = new Random();
	   
	   for (int i=0; i<10; i++) {
              A[i] = 2+r.nextInt(3);
           }
           for (int i=0; i<10; i++) {
              System.out.println(A[i]);
           }
 

        9) check if a value 0 is in the array A, display "zero" if yes,
        and "no 0" if no.
        
      boolean z = false;
      for (int i=0; i<10; i++) {
	      if (A[i]==0) {
	         z=true; break;
	      }
	   }
	  if (z) {
		 System.out.println("Zero!");
	  }
	  else {
		 System.out.println("No zero.");
      }
    
       10)  Compute A+B, A-B, A*B and display the results.
	
	   For example, let array A={1,2,3}, B={2,1,3}.  
	   A+B={1+2,2+1,3+3}={3,3,6};   A-B={1-2,2-1,3-3}={-1,1,0};
	   
	   
	   
	   
	   // note the condition of matrix multiplication.
	   A*B' ={1 2 3}*{2 
	                  1
	                  3}
	        ={1*2+2*1+3*3} 
	        = {13}; 
	        
	   A'*B = {1  
	           2
	           3}{2 1 3}= {1*2, 1*2, 1*3  = {2,1,3
	   		       2*2, 2*1, 2*3     4,2,6
	   		       3*2, 3*1, 3*3}    6,3,9}
	   
	   ---------
	       class multiplication1 {

		  public static void main(String [] args) {

		    int [][] C = new int [3][3];

		    int A[]={1,2,3}; int B[]={2,1,3};
		    for (int i=0; i<3; i++) {
		       for (int j=0; j<3; j++) {
			  C[i][j] = A[i]*B[j];
		       }
		    }
		    for (int i=0; i<3; i++) {
		       for (int j=0; j<3; j++) {
			  System.out.print(C[i][j]+"  ");
		       }
		       System.out.println();
		    }
		   }
		}
	   ------------	        
	   				        
	    a) C=A+B, and D=A-B:
	  
	  ---------
		   int [] A = new int [3];
		   int [] B = new int [3];
		   int [] C = new int [3];
		   int [] D = new int [3];

		   for (int i=0; i<3; i++) {
			  C[i] = A[i]+B[i];
			  D[i] = A[i]-B[i];
		       }

		    b) two-dimensional array:

		    import java.util.Random;

		    int [][] C = new int [3][3];
		    int [] A = new int [3];
		    int [] B = new int [3];

		    Random r = new Random();

		    for (int i=0; i<3; i++) {
			  A[i] = 1+r.nextInt(2);
			  B[i] = 1+r.nextInt(2);
		       }

		    for (int i=0; i<3; i++) {
		       for (int j=0; j<3; j++) {
			  C[i][j] = A[i]*B[j];
		       }
		    }	    
		    for (int i=0; i<3; i++) {
		       for (int j=0; j<3; j++) {
			  System.out.println(C[i][j]);
		       }
		    }	    
	----------
          
III. Implementation:

Problem 1)

----
  class test1 {
     public static void main(String [] args) {
        int [] A = new int [100];
        for (int i=1; i<10; i++) {
  		  System.out.println(A[i]);
  	  }
     }
  }
----

Problem 2) 
-----
import java.util.Random;

class test2 {
   public static void main(String [] args) {
	  Random r = new Random();

      int [] A = new int [100];

      for (int i=0; i<10; i++) {
		  A[i]=r.nextInt(10);
	  }

	  for (int i=0; i<10; i++) {
	  	  System.out.println(A[i]);
	  }

	  System.out.println("2:"+A[2]+"  "+"4:"+ A[4]);


   }
}
-----

Problem 3):

----
import java.util.Random;

class test3 {
   public static void main(String [] args) {
	  Random r = new Random();

      int [] A = new int [100];

      for (int i=0; i<10; i++) {
		  A[i]=r.nextInt(10);
	  }


      for (int i=0; i<10; i++) {
		  System.out.println(i+"\t"+A[i]);
	  }

      int i = r.nextInt(9);

	  System.out.println(i+": "+A[i]);

   }
}

----

Problem 4)

----
import java.util.Random;

class test4 {
   public static void main(String [] args) {
	  Random r = new Random();

      int [] A = new int [100];

      for (int i=0; i<10; i++) {
		  A[i]=r.nextInt(10);
	  }


      for (int i=0; i<10; i++) {
		  System.out.println(i+"\t"+A[i]);
	  }

   }
}
----

Problem 5)

----
import java.util.Random;

class test5 {
   public static void main(String [] args) {
	  Random r = new Random();

      int [] A = new int [100];

      for (int i=0; i<10; i++) {
		  A[i]=r.nextInt(10);
	  }


      for (int i=0; i<10; i++) {
		  System.out.println(i+"\t"+A[i]);
	  }
	  System.out.println();

      for (int i=9; i>=0; i--) {
		  System.out.println(i+"\t"+A[i]);
	  }


   }
}
----

Problem 6)

----
import java.util.Random;

class test6 {
   public static void main(String [] args) {
	  Random r = new Random();

      int [] A = new int [100];

      for (int i=0; i<10; i++) {
		  A[i]=r.nextInt(10);
	  }


      for (int i=0; i<10; i++) {
		  System.out.println(i+"\t"+A[i]);
	  }
	  System.out.println();

	  int total = 0;
      for (int i=3; i<9; i++) {
		  total = total + A[i];

	  }
	  System.out.println("total A[3..8]=\t"+total);


   }
}
----

Problem 7)

----
import java.util.Scanner;

class test7 {

   public static void main(String [] args) {

      int [] A = new int [100];

	  Scanner keyboard = new Scanner(System.in);

	  for (int i=0; i<10; i++) {
		  A[i] = keyboard.nextInt();
	  }
	  for (int i=0; i<10; i++) {
		  System.out.println(A[i]);
      }
      System.out.println();

      for (int i=0; i<10; i++) {
		  System.out.println(i+"\t"+A[i]);
	  }
	  System.out.println();

   }
}
----

Problem 8)

----
import java.util.Random;

class test8 {

   public static void main(String [] args) {

      int [] A = new int [100];

	  Random r = new Random();

	  for (int i=0; i<10; i++) {
              A[i] = 2+r.nextInt(3);
      }


	  for (int i=0; i<10; i++) {
		  System.out.println(A[i]);
      }
      System.out.println();

      for (int i=0; i<10; i++) {
		  System.out.println(i+"\t"+A[i]);
	  }
	  System.out.println();

   }
}
----

Problem 9)

----
import java.util.Random;

class test9 {

   public static void main(String [] args) {

      int [] A = new int [100];

	  Random r = new Random();

	  for (int i=0; i<10; i++) {
              A[i] = r.nextInt(10);
      }

	  for (int i=0; i<10; i++) {
		  System.out.println(i+"\t"+A[i]);
      }
      System.out.println();

      boolean z = false;
      for (int i=0; i<10; i++) {
	      if (A[i]==0) {
	         z=true; break;
	      }
	   }
	  if (z) {
		 System.out.println("Zero!");
	  }
	  else {
		 System.out.println("No zero.");
      }

   }
}
----

Problem 10)a):

----
import java.util.Random;

class test10a {

   public static void main(String [] args) {

      int [] A = new int [100];
      int [] B = new int [100];

	  Random r = new Random();

	  for (int i=0; i<10; i++) {
              A[i] = 1+r.nextInt(9);
              B[i] = 1+r.nextInt(9);
      }


	  for (int i=0; i<10; i++) {
		  System.out.println(i+":\t"+A[i]+"\t"+B[i]);
      }
      System.out.println();

      for (int i=0; i<10; i++) {
		  System.out.println(i+"\t"+A[i]+"+"+B[i]+"=\t"+(A[i]+B[i]));
	  }
	  System.out.println();

   }
}
----

Problem 10)b):

----
import java.util.Random;

class multiplication {

   public static void main(String [] args) {

	    Random r = new Random();

 	    int [][] C = new int [3][3];
		int [] A = new int [3];
		int [] B = new int [3];

		for (int i=0; i<3; i++) {
			  A[i] = 1+r.nextInt(2);
			  B[i] = 1+r.nextInt(2);
		}

		for (int i=0; i<3; i++) {
			  System.out.print(A[i]+" ");
		}
		System.out.println();


		for (int i=0; i<3; i++) {
			  System.out.print(B[i]+" ");
		}
		System.out.println();

	    for (int i=0; i<3; i++) {
	       for (int j=0; j<3; j++) {
	          C[i][j] = A[i]*B[j];
	       }
	    }
	    for (int i=0; i<3; i++) {
	       for (int j=0; j<3; j++) {
	          System.out.print(C[i][j]+"  ");
	       }
	       System.out.println();
	    }
    }
}
-----------------