Pascal's Triangle II

Problem: Pascal's Triangle II

To do this in O(k) extra space, we simply use one list to represent each row. We add the latter number to the former number and add 1 to the head of the list.

Code in Python:

class Solution(object):
    def getRow(self, rowIndex):
        """
        :type rowIndex: int
        :rtype: List[int]
        """
        res = [1]
        for k in xrange(rowIndex):
            for i in xrange(len(res)-1):
                res[i] += res[i+1]
            res = [1] + res
        return res