119. Pascal’s Triangle II

Given a non-negative index k where k ≤ 33, return the k^th index row of the Pascal’s triangle.

Note that the row index starts from 0.

In Pascal’s triangle, each number is the sum of the two numbers directly above it.

Example:

Input: 3
Output: [1,3,3,1]

Follow up:

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

Python

 
class Solution(object):
    def getRow(self, rowIndex):
        """
        :type rowIndex: int
        :rtype: List[int]
        """
        rowIndex +=1
        row_list = []
        for i in range(1, rowIndex+1):
            row_list.append(self.return_result(i,rowIndex))
        return row_list


    def return_result(self, a, row_num):
        return self.factorial(row_num-1)/(self.factorial(a-1)*self.factorial(row_num-a))

    def factorial(self, n):
        return reduce(lambda x, y: x * y, [1] + range(1, n + 1))