【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?

思路：每次用记录的值带入下一次计算。

class Solution {public:    vector<int> getRow(int rowIndex){        vector<int> ret;        int i = 0;        long long num = 1;        int n = rowIndex;        for(;i<=rowIndex;){            ret.push_back(num);            i++;            num = num*n/i;            n--;        }        return ret;    }};