BlueJ program on Pascal triangle using 2 d array

We know that Java arrays are dynamic and 2 d array can be constructed with different number of columns. In this program we will create the 2 d array with 5 rows aned afterwards for the 1^st row number of columns will be 1, for the second rwo number of columns will be 3 and so on.

While creating the number of columns for each row of the 2 d array, the ist column and the last column of each row will be filled up with 1.

Next job is to fill up the vacant columns of rows starting from number 2 with previous rows values. And the sequence is like   arr[i][j]=arr[i-1][j-1] + arr[i-1][j], arr[i][j+1]=arr[i-1][j] + arr[i-1][j+1]and so on. After filling up the 2 d array, display the 2 d array.

 Here is the program:

class Pascal

{

 int arr[][]=new int[5][];

 int i,j,k;

 Pascal()

 {

 arr[0]=new int [1];

 arr[0][0]=1;

 arr[1]=new int [2];

 arr[1][0]=1;

 arr[1][1]=1;

 arr[2]=new int [3];

 arr[2][0]=1;

 arr[2][2]=1;

 arr[3]=new int [4];

 arr[3][0]=1;

 arr[3][3]=1;

 arr[4]=new int [5];

 arr[4][0]=1;

 arr[4][4]=1;

}

void show()

{

 for(i=0;i< 5;i++)

 {

 for(k=i;k< 5;k++)

 {

  System.out.print(" ");

  }

  for(j=0;j< =i;j++)

 {

   System.out.print(arr[i][j]+ " ");

 }

   System.out.println();

}

}

void set()

{

 for(i=2;i< 5;i++)

 {

  for(j=1;j< i;j++)

  {

   arr[i][j]=arr[i-1][j-1]+arr[i-1][j];

  }

  }

 }

 public static void main(String agrs[])

 {

  Pascal ob=new Pascal();

  System.out.println(" Traingle with values at start and end of row only\n");

 

  ob.show();

  ob.set();

  System.out.println(" Final array\n");

  ob.show();

  }

  }

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