LeetCode Array Easy 119. Pascal's Triangle II

Given a non-negative index k where k ≤ 33, return the kth index row of the Pascal's triangle.

Note that the row index starts from 0.

In Pascal's triangle, each number is the sum of the two numbers directly above it.

Example:
Input: 3
Output: [1,3,3,1]
Follow up:

Could you optimize your algorithm to use only O(k) extra space?

题目描述，给定一个行的索引值，返回当前行的帕斯卡三角当前行的值。

进阶：在O(k)的空间复杂度上完成

思路：在思考在O(k)的空间复杂度上实现未果，转而使用普通实现。用两个数组来实现，一个数组prev负责保存保存上一行的数，用来计算下一行的值，最终计算出要求的行的数。

C#解法：

 public IList<int> GetRow(int rowIndex) {
        int[] prev = null;
            List<int> result = new List<int>();
            if (rowIndex == 0)
                result.Add(1);
            else
            {

                result.AddRange(new int[] { 1, 1 });
                while (rowIndex > 1)
                {
                    prev = result.ToArray();
                    
                    result.Clear();
                    result.Add(1);
                    for (int i = 0; i < prev.Length - 1; i++)
                    {
                        int val = prev[i] + prev[i + 1];
                        result.Add(val);
                    }
                    result.Add(1);
                    rowIndex--;
                }
                
            }
            return result;
    }

还是没能在O(k)的空间复杂度下计算出来，继续努力