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Pascal's Triangle II

描述

Given an index k, return the k-th 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?

分析

滚动数组。

代码

// Pascal's Triangle II
// 滚动数组,时间复杂度O(n^2),空间复杂度O(n)
public class Solution {
public List<Integer> getRow(int rowIndex) {
List<Integer> array = new ArrayList<>();
for (int i = 0; i <= rowIndex; i++) {
for (int j = i - 1; j > 0; j--){
array.set(j, array.get(j - 1) + array.get(j));
}
array.add(1);
}
return array;
}
}

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