LeetCode 119. Pascal's Triangle II

问题描述

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?

题目描述

给定一个数，返回杨辉三角中对应的行。只能用O（n）的复杂度。这个题目使用一行数据，从最后一位开始计算杨辉三角的值。

算法实现

public List<Integer> getRow(int rowIndex) {
int num = rowIndex + 1;
int[] row = new int[num];
for (int i = 0; i < num; i++) {
row[0] = 1;
row[i] = 1;
for (int j = i - 1; j >= 1; j--) {
row[j] = row[j] + row[j - 1];
}
}
List<Integer> result = new ArrayList<Integer>();
for (int n : row) {
result.add(n);
}
return result;
}