Write methods with the following headers 1. public static int[] twoDimensionalTo

Question

Write methods with the following headers
1. public static int[] twoDimensionalToOneDimensional(int[][] arr)
- if arr is null then this method returns null
- if arr is not null then (i) copy the rows of arr to a one-dimensional array
and (ii) return the one-dimensional array.
- the length of the return array should be equal to the number of values
stored in arr
Copy the rows in ascending order. In other words, first copy row 0 to the
one-dimensional array, then row 1, 2, etc.
Example:
Assume int[][] arr = { { 1,20, 50}, {5, 8}, {22, 100, 200, 1}};
Also assume we have the variable
int[] returnArray
If we copy the contents of arr to returnArray, then returnArray contains
the following values:
{ 1, 20, 50, 5, 8, 22, 100, 200, 1};
Suggestion: Each row of arr may have a different number of columns. If
arr isn

Explanation / Answer

comment if you have any doubts.

public class HW1 {

   public static void display(int[] arr) {
       for (int x : arr) {
           System.out.print(x + " ");
       }
       System.out.println();
   }

   public static void main(String[] args) {

       int[][] numbers = { { 7, 6, 5, 3, 2, 1 }, { 109 }, { -77, 61, 2 } };

       int[] output = twoDimensionalToOneDimensional(numbers);
       if (output == null) {
           System.out.println("The 1-D array is null");
       } else {
           display(output);
       }
       System.out.println();
       numbers = null;
       output = twoDimensionalToOneDimensional(numbers);
       if (output == null) {
           System.out.println("The 1-D array is null");
       } else {
           display(output);
       }
       System.out.println();
       int[] x = {3, 4, 8, -1, 2, 4};;
       display(x);
       rotateArray(x, 2);
       display(x);
       System.out.println();
   }
   public static int[] twoDimensionalToOneDimensional(int[][] arr)
   {
       if(arr==null)return null;
       int newlength=0;
       for(int i=0;i<arr.length;i++)
       {
           for(int j=0;j<arr[i].length;j++)
               newlength++;
       }
       int newarr[]=new int[newlength];
       int num=0;
       for(int i=0;i<arr.length;i++)
       {
           for(int j=0;j<arr[i].length;j++)
               {newarr[num]=arr[i][j];num++;}
       }
       return newarr;
   }
   public static void rotateArray(int[] arr, int rotate)
   {
       if(arr!=null)
       {
           int dummy[]=new int[arr.length];
           for(int i=0;i<arr.length;i++)
           {
               int dum=arr.length+i-rotate;
               if(dum >= arr.length)dum=dum-arr.length;
               dummy[i]=arr[dum];
           }
           for(int i=0;i<arr.length;i++)
               arr[i]=dummy[i];
       }
   }

}

//output:

7 6 5 3 2 1 109 -77 61 2

The 1-D array is null

3 4 8 -1 2 4
2 4 3 4 8 -1

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