[leetcode] 119 Pascal Triangle 2 c++

// http://leetcode.com/onlinejudge#question_119
/*
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:
    vector<int> getRow(const int rowIndex) {
        typedef std::vector<int> row_t;
        typedef std::vector<row_t> tri_t;

        row_t prev(rowIndex+1,1), curr(rowIndex+1,1);

        for(int row_no = 0; row_no < rowIndex+1; ++row_no)
        {
            std::swap(prev,curr);

            curr[0] = curr[row_no] = 1;
            for(int j = 1; j < row_no; ++j)
            {
                curr[j] = prev[j-1] + prev[j];
            }

        }


        return curr;

    }
};