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?

分析：细节实现题。代码如下：

class Solution {public:    vector
     
       getRow(int rowIndex) {        if(rowIndex == 0) return vector
      
       (1,1);                vector
       
         result(2,1);        for(int i = 3; i <= rowIndex+1; i++){            vector
        
          next;            next.push_back(1);            for(int j = 1; j < i-1; j++){                next.push_back(result[j-1] + result[j]);            }            next.push_back(1);            result = next;        }        return result;    }};