119. Pascal's Triangle II*

Given an index k, return the kth row of the Pascal's triangle.

For example, given k = 3,

Return

[1,3,3,1]

.

Note:

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

Reference

class Solution(object):
def getRow(self, rowIndex):
"""
:type rowIndex: int
:rtype: List[int]
"""
result = [0]*(rowIndex+1)
result[0]= 1
for i in range(1,rowIndex+1):
for j in range(i,0,-1):
result[j] +=result[j-1]
return result

Note:
It is obvious that we should find the law of numbers in certain row of Pascal's Triangle.

According to materials online, the nth number in mth row is C(m,n-1).However, this method needs a lot of computation.