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?

Solution: from back to forth...

 1 class Solution {
 2 public:
 3     vector<int> getRow(int rowIndex) {
 4         vector<int> res(rowIndex+1, 1);
 5         for(int i = 1; i <= rowIndex; i++) {
 6             for(int j = i-1; j >= 1; j--) {
 7                 res[j] += res[j-1]; 
 8             }
 9         }
10         return res;
11     }
12 };

 

posted @ 2014-04-12 03:38  beehard  阅读(88)  评论(0)  编辑  收藏  举报