LeetCode刷题笔录 Pascal's Triangle II

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?

这题比较简单，知道公式是就没什么问题了。用一个temp数组存储前一轮的结果即可。

似乎是人生第一次在没用IDE的情况下一遍通过，庆贺一下

public class Solution {
    public ArrayList<Integer> getRow(int rowIndex) {
        int[] temp = new int[rowIndex + 1];
        int[] result = new int[rowIndex + 1];
        //set the first row with an 1 at the beginning and followed by zeroes
        temp[0] = 1;
        result[0] = 1;
        for(int i = 1; i <= rowIndex; i++){
            temp[i] = 0;
            result[i] = 0;
        }
        
        for(int n = 1; n <= rowIndex; n++){
            for(int k = 0; k <= rowIndex; k++){
                if(k == 0){
                    result[k] = 0 + temp[k];
                }
                else{
                    result[k] = temp[k] + temp[k - 1];
                }
            }
            //copy the content of result into temp array for the next iteration
            System.arraycopy(result, 0, temp, 0, rowIndex + 1);
        }
        
        ArrayList<Integer> res = new ArrayList<Integer>(rowIndex + 1);
        for(int i = 0; i <= rowIndex; i++){
            res.add(result[i]);
        }
        return res;
    }