leetcode - 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?

class Solution {public:    std::vector<int> getRow(int rowIndex) {        std::vector<int> triangle(rowIndex + 1);triangle[0] = 1;for(int i = 1; i <= rowIndex; i++){for(int j = i; j >= 0; j--){if(i == j) triangle[j] = triangle[j-1];else if(j) triangle[j] += triangle[j-1];}}return triangle;    }};