Pascal's Triangle II

Problem Statement

Given an index k, return the kth row of the Pascal's triangle.

For example, given k = 3,
Return [1,3,3,1].

Note:
Could you optimize your algorithm to use only O(k) extra space?

Link to GitHub :link

Pascal’s Triangle

Pascal’s triangle is a triangular array of the binomial coefficients. Write a function that takes an integer value n as input and prints first n lines of the Pascal’s triangle. Following are the first 6 rows of Pascal’s Triangle.

ex of pascal triangle

1  
1 1 
1 2 1 
1 3 3 1 
1 4 6 4 1 
1 5 10 10 5 1 

Solution

• We need arrarlist
• This arraylist row is used to add initial elements of the array

          row.add(0, 1)
          Note for the first 2 iterations elements would not be altered before adding to allrows

          {1},{1,1}

• J loop iteration would not start till Row Size is greater than one. It is responsible to altering the arrraylist elements so to generate pascal triangle

         {1},{1,1},{1,2,1}

• The contents of the arraylist would be modified based on the size of the array.

public class PascalTriangle2 {
 
 public static List<Integer> get(int rowIndex){
  
  //Declare a new List
  List<Integer> list=new ArrayList<Integer>();
   
  if(rowIndex <0)
  {
   return list;
  }
  //Creation of Pascal triangle list
  for(int i=0;i< rowIndex+1;i++) 
  {
   list.add(0,1);
   for(int j=1;j<list.size()-1;j++)
   {
    list.set(j, list.get(j)+list.get(j+1));
   }
  }
  return list;
 }