Pascal’s Triangle II

Desicription

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

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class Solution {
private:
    int C(double A, double B) {
        double res = 1;
        for(int i = 1; i <= B; i++)
            res *= (double)(A-i+1)/i;
        return res+0.5;
    }
public:
    vector<int> getRow(int rowIndex) {
        vector<int> res;
        for(int i = 0; i <= rowIndex; i++)
            res.push_back(C(rowIndex, i));
        return res;
    }
};