119. Pascal’s Triangle II-杨辉三角 II

Given an integer rowIndex, return the rowIndex-th row of the Pascal’s triangle.

Notice that the row index starts from 0.

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

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

Example 1:
Input: rowIndex = 3
Output: [1,3,3,1]

Example 2:
Input: rowIndex = 0
Output: [1]

Example 3:
Input: rowIndex = 1
Output: [1,1]

Constraints:

• 0 <= rowIndex <= 33

Solution in python:

class Solution:
    def getRow(self, rowIndex: int) -> List[int]:
        result = [1]
        if rowIndex == 0:
            return result
        while rowIndex > 0:
            for i in range(len(result)-1):
                result[i] = result[i] + result[i+1]
            result.insert(0, 1)
            rowIndex -= 1
        return result