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?

杨辉三角 II

自上到下行行计算

class Solution(object):
    def getRow(self, rowIndex):
        """
        :type rowIndex: int
        :rtype: List[int]
        """

        nums = []
        for i in range(rowIndex+1):
            nums = [nums[j - 1] + nums[j] for j in range(1, i)]
            nums.insert(0, 1)

            if i != 0:
                nums.append(1)
        return nums