Arithmetic Triangle

Arithmetic Triangle

Difficulty: Easy

Given an integer numRows, return the first numRows of Arithmetic's triangle.

In Arithmetic's triangle, each number is the sum of the two numbers directly above it as shown:

Solution: 

Java

class Solution {

    List<List<Integer>> list;

    public List<List<Integer>> generate(int numRows) {

        list=new ArrayList<>();

        if(numRows==0)

            return list;

        list.add(new ArrayList<Integer>(Arrays.asList(1)));

        for(int i=1;i<numRows;i++){

            List<Integer> l=new ArrayList<Integer>();

            List<Integer> prev=list.get(i-1);

            for(int j=0;j<=i;j++){

                if(i==0||j==0||i==1||i==j){

                    l.add(1);

                    continue;

                }

                l.add(prev.get(j)+prev.get(j-1));

            }

            list.add(l);

        }

        return list;

    }

}

Contributed By: Mohammed Raeesul Irfan CSE

Python

class Solution:

   def generate(self, numRows: int) -> List[List[int]]:

        if numRows == 0:

            return []

        if numRows == 1:

            return [[1]]

        res = [[1]*i for i in range(1,numRows+1)]    

        for i in range(1,numRows):

            for j in range(1,i):

                res[i][j] = res[i-1][j-1]+res[i-1][j]

        print(res)

        return res