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?

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class Solution { public: vector<int> getRow(int rowIndex) { vector<int> result; int n = rowIndex / 2; result.push_back(1); for(int i = 1; i <= n; i++){ long long next = (long(result[i - 1]) * long(rowIndex - i + 1)) / i; result.push_back(next); } if(rowIndex % 2 == 1){ int size = result.size(); for(int i = size - 1; i >= 0; i--){ result.push_back(result[i]); } }else{ int size = result.size(); for(int i = size - 2; i >= 0; i--){ result.push_back(result[i]); } } return result; } };