[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?

动规不解释。

class Solution {
public:
    vector<int> getRow(int rowIndex) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        int *a = new int[rowIndex+1];
        vector<int> v;
        for(int i = 1;i <= rowIndex+1;i++)
        {
            for(int j = i - 1;j >= 0;j--)
            {
                if(j == 0)
                    a[j] = 1;
                else if(j == i-1)
                    a[j] = 1;
                else
                    a[j] = a[j]+a[j-1];
            }
        }
        for(int j = 0;j <= rowIndex;j++)
            v.push_back(a[j]);
        return v;
    }
};