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?

Answer:

class Solution {public:    vector<int> getRow(int rowIndex) {           vector<int> ivc;        ivc.push_back(1);        if(rowIndex == 0) return ivc;        for(int i = 1; i <= rowIndex; i ++)        {            ivc.push_back(1);            int isz = ivc.size()-1;            for(int j = isz-1; j >=1; j --)            {                ivc[j] = ivc[j-1]+ivc[j];            }        }        return ivc;    }};