119. Pascal's Triangle II.py

# Given a non-negative index k where k ≤ 33, return the kth 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?

class Solution(object):
    def getRow(self, rowIndex):
        """
        :type rowIndex: int
        :rtype: List[int]
        """
        ans = [1]
        for i in range(rowIndex):
            ans = [x+y for x, y in zip([0]+ans, ans+[0])]
        return ans