LeetCode | Pascal's Triangle II

题目

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?

题目要求只用O(k)额外空间，其实分析下杨辉三角的计算方式，就知道只要O(1)的额外空间就行了。

代码

import java.util.ArrayList;

public class PascalsTriangleII {
	public ArrayList<Integer> getRow(int rowIndex) {
		ArrayList<Integer> results = new ArrayList<Integer>();
		results.add(1);
		for (int i = 1; i <= rowIndex; ++i) {
			int temp = 1;
			for (int j = 1; j < i; ++j) {
				int innerTemp = results.get(j);
				results.set(j, temp + results.get(j));
				temp = innerTemp;
			}
			results.add(1);
		}
		return results;
	}
}

LeetCode | Pascal's Triangle II

原文：http://blog.csdn.net/perfect8886/article/details/19918029