Pascal's Triangle II

Problem

Given an index k, return the kth row of the Pascal's triangle.

For example, given k = 3,
Return [1,3,3,1].

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Idea

这个题目要求memory O(k)。所以只能用1维数组来做。发现row[i] = row[i]+row[i-1] 左边是下一行的row[i]，右边是上一行的row[i]和row[i-1]

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Solution

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