119. 杨辉三角2 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?

题意：计算杨辉三角的某一行，要求空间复杂度为O(k)

public class Solution {
    public IList<int> GetRow(int rowIndex) {
        List<int> result = new List<int>();
        if (rowIndex >= 0) { result.Add(1); }
        if (rowIndex >= 1) { result.Add(1); }
        for (int index = 2; index <= rowIndex; index++) {
            result.Add(1);
            for (int i = index - 1; i >= 1; i--) {
                result[i] = result[i] + result[i - 1];
            }
        }
        return result;
    }
}

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